Best and Worst Defensive Pokemon In-Game

[DrumstickGaming]

So it's no secret that defensive Pokemon often get overlooked for in-game playthroughs which are usually all-about offense. When I think of awkward defensive Pokemon I think of this mon

Bronzor is somehow both really annoying when you use it and really annoying when the computer uses it. To my memory essentially every NPC Bronzor/Bronzong has Levitate and thus are all weak to Fire, a fairly rare type even when Platinum's dex is taken into consideration. Gets status moves and Extrasensory early, is hard to hit for weakness, so you'd think this mon would be surprisingly good for your team, right?

...Not really. Looking at Platinum boss rosters a distressing amount of mons hit Bronzong neutrally, a big yikes when your offensive dual STAB almost never hits SE. It's such a shame because on paper Bronzong sounds incredible, but its resistances are bizarrely ill-suited to the region it is found in. Even when you have the occasional trainer Bronzong can kinda wall, it's still Bronzong so it's not like you're killing anything. Man this mon would kill for a decent recovery move.

Let's contrast this to Magnezone. While not built like a wall like Bronzong, Magnezone has a noticeably better defensive typing, 130 Special Attack Thunderbolt (in its home game boosted by Choice Specs), and just rocks the second half of the game as long as nothing has Earthquake. In other games (BW2/Alola) it does have trouble dealing damage until the later levels but the defensive type and Thunder Wave give it some use.

What are some defensive mons you guys think are underwhelming or surprisingly good in-game?

 

[Castersvarog]

Toxepex is my first go to for a bad ingame mon, especially when its a great mon competitively but it falls off so badly.
Tbh, In-game has never really been kind to the pure wall mons to begin with until Body Press happened. Other trainer fights rarely output enough damage that you'd need a legit wall to survive, a type resistance is often more then enough to tank, and using a mon, like the Magnezone you mention, with good offense and defenses does the job perfectly fine letting you just win fights faster.

Meanwhile, your walls basically need to have a ton of defense investment to do a good enough job of tanking anyway, and are built around slow chip damage, but that means it takes forever to beat an opponent. Meanwhile a Sweeper or anything with a decent offensive stat can 2-3 hit ko most everything

 

[Suspicious Derivative]

Skarmory is usually a good Pokémon for competitive battling, but I have had success with it in-game as well. I used it when I replayed Crystal last year and it was better than I expected. Despite some notable shortcomings such as being available late and having a bad offensive movepool, I found it great. Since it isn't obtainable until late in Johto, it only really saw use against Clair and the E4 during the main game. But it was very good during the post-game in Kanto.

Sky-high Defense combined with a ton of resistances is solid, the most notable being that it resists Normal which is great since it felt like Normal is the most common offensive type in Gen 2. It is also a hard block to Grass (which was very helpful for me since the rest of my team were all water-types), and immunities to both Poison and Ground is nice as well. The two weaknesses to Fire and Electric didn't really matter much since those are pretty uncommon types, and they were covered by the rest of my team anyway. Skarmory doesn't hit super hard, and it doesn't learn Steel Wing until level 49 (which for me was right at the end of Kanto), but Fly was usually enough to get the job done. I don't know how good Skarmory is for in-game use in other generations, but it definitely surpassed my expectations in Crystal.

 

[CryoGyro]

Even calling Pachirisu 'defensive' might be a stretch going by its raw stats, but it's a deceptively solid Pokemon in the context of DPP. You've probably noticed when battling it that it's miles ahead of most Pokemon at Valley Windworks in bulk and Speed; the Eterna Forest Lass's Pachirisu kills Piplup speedruns for more reasons than just type matchup. It's a much more effective and interesting Bide user than Kricketot for the couple of levels before Spark, at which point it can use Electric's excellent early to mid-game matchup spread to compensate for its tiny attack stats. Compared to Shinx, learning Grass Knot from Gardenia means it doesn't have to stay away from Hikers, and it learns Discharge much faster for greater team support potential. You'll start to really notice its weak attacks by the second half of the game, but enough fodder is weak to Electric that it can keep up, and endgame Charge Beam means you can even have a hilarious Elite Four run. It's no gamebreaker, but a more competent part of a team than you probably expect, a fun novelty for an early Electric-type over Shinx, and a great example of how Pokemon shouldn't be entirely evaluated by their data pages.

 

[CTNC]

The Absolute Best Defensive Pokemon: Shedinja
The hypothetical best defense is absolute immunity to everything. Against a lot of Pokemon, Shedinja is immune to everything. If the opponent has any Pokemon who can't do anything to Shedinja, you don't need to worry about those Pokemon. After everything that can touch Shedinja is down, you win.

The Absolute Worst Defensive Pokemon: Shedinja
You'd be amazed how many random moves happen to hit it. Do you know how many Pokemon learn Bite?


For Pokemon that are definitely good, Anything with Leech Seed. Anything.

Using Status Moves Only may have lead me to being obsessed with that move... Anyway, passive healing can turn good tanks into insanely good ones and Protect just amplifies how good Leech Seed can be. Healing for 1/8 of the opponent's HP every turn AND Protect making you only take attacks every other turn means so many Pokemon can barely do anything to you and you can do whatever, like setting up Toxic Spikes. If you add in Leftovers, you'll see why I don't use Leftovers in game any more. Oh, and if the Leech Seed user turns out to have a bad matchup against whatever Leech Seed is used on, switching will make whatever's sent out get healed, so Pokemon that learn Leech Seed are like a cross between a really good tank and a suporter who can amplify another tank. Leech Seed is why I use multipule Grass types on playthroughs. It makes any Pokemon that good.

 

[WarriorGallade]

Toxepex is my first go to for a bad ingame mon, especially when its a great mon competitively but it falls off so badly.
Tbh, In-game has never really been kind to the pure wall mons to begin with until Body Press happened. Other trainer fights rarely output enough damage that you'd need a legit wall to survive, a type resistance is often more then enough to tank, and using a mon, like the Magnezone you mention, with good offense and defenses does the job perfectly fine letting you just win fights faster.

Meanwhile, your walls basically need to have a ton of defense investment to do a good enough job of tanking anyway, and are built around slow chip damage, but that means it takes forever to beat an opponent. Meanwhile a Sweeper or anything with a decent offensive stat can 2-3 hit ko most everything

Kinda disagree with this - I recently played through a run of Moon with no evolving or fully evolved mons, and Mareanie was a very solid midgame backbone for my team, with access to Toxic, Toxic Spikes and Recover naturally (notably, without using Eviolite). If I'd chosen to evolve it just as its bulk started to waver (around the final Guzma fight), it would've been incredibly potent in-game in terms of just stalling out everything, and this was without Regenerator too. If you get one with Merciless like what I did, it also ends up being able to take on an offensive role, as it easily cleaves through the final Lusamine's lead Clefable, which can be quite the challenge given how it has Magic Guard + Cosmic Power.

But as for my own answer to this, the pick for a great defensive mon would be Shieldon, who I also used in that same playthrough. It's remarkably bulky for the stage in-game where you receive it at (with an early-ish evo level too), and while its own offensive stats are low, you can usually use Metal Sound to get around that and chip with Ancient Power - a held Sitrus Berry is surprisingly effective for longevity too. It makes for a pretty great defensive combination with Mareanie because it learns Protect naturally, and resists or is neutral to a lot of types that would give Mareanie trouble (besides Ground). Pretty good way to stall for time while Toxic Spikes take hold. And of course, when you get Metal Burst, it's a very good way to force a 1 for 1 trade (or at least, significantly damage them) against a Pokemon you have no chance of outspeeding, especially if it's in a game with modern Sturdy.

 

[Ironmage]

BDSP lets Skorupi be readily available via the Grand Underground as soon as the player reaches Eterna City, rather than being locked to a finicky spawn in the Great Marsh. Not only is base 90 Defense and a potential crit immunity really noticeable at this point in the game, Bug/Poison also double resists the next two gyms' main types. A relatively late evolution level of 40 does mean it sometimes doesn't get Drapion's Dark type by the Ghost gym, but Poison/Dark also defensively answers nearly everything Team Galactic can throw at you (they mostly have Psychics, Darks, and Poisons of their own). Being a Dark type without a weakness to Bug or Fairy is also pretty relevant for an Elite Four team.

 

[bdt2002]

Possibly a cliché example, but I feel like these three still aren’t quite as bad as they’re made out to be. I never said they were super strong in-game, but I can’t quite call them “the worst starter ever” or anything like that. Meganium once it’s fully evolved is actually quite difficult for most NPCs to take down, and while it won’t be doing as much damage as the other starters and prefers a slower pace of play, this evolution family rewards skill and knowledge of the game with a defensive backbone for your team to take advantage of. Maturing is realizing that it’s not Chikorita itself that is bad; it’s that Grass typing that’s holding it back. A hypothetical Water-Type Meganium may feel like it would be too similar to Suicune, I’ll admit, but a Fire-Type Meganium would almost certainly be one of the best defensive Pokémon in the entire game. Grass really is just that bad in Gens 2 and 3.

 

[QuentinQuonce]

Vespiquen in DPP. Yes getting a female Combee is a pain, but Combee - unlike a lot of other weak Pokemon who need a little babying - isn't actually terrible to raise since Gust is a serviceable move for the early-game due to all the Bug- and Grass-type Pokemon in Eterna Forest/City. Odds are you'll catch one at least in the early teens, and it evolves early enough that it won't be a Combee for very long.

And despite her terrible typing, Vespiquen is pretty formidable. Power Gem at level 21 is incredibly good - it needs TMs or move tutors/reminders to be fantastic since it has to wait a bit too long for a decent Bug move, but Toxic and Heal Order do a lot for it. Base 102 defensive stats are crazy for something that evolves so early, and it makes Vespiquen a pretty darn good wall against a lot of what Sinnoh throws at you. Less so in Platinum, admittedly, where there's more Fire-types and opponents generally pack a bit more offensive coverage, but it's still a great option nonetheless.

Plus it's just incredibly fun to use. Kind of in the same vein as Magikarp and Feebas as a "this needs time investment to find and raise" sort of Pokemon, but neither as brutally strong as Gyarados gets or as grindingly difficult as Milotic is to evolve.



Hot take for RSE: Dustox. I've used this a few times and... well, I'd hardly call it one of the best defensive Pokemon ever, buuuut... it honestly ain't half bad for an in-game run. Well... with some caveats.

It has a lot of surprising positives. Shield Dust is an underrated ability: being immune to random flinch/paralysis is huge, especially considering it can tank a lot of neutral Special moves thanks to its decent bulk. And it's one of the better options against Brawly's gym thanks to Gust and Confusion. It gets a bunch of useful supportive options (Protect, Moonlight, Whirlwind, Light Screen, Flash) while the attacking moves it does learn either have a chance of confusing the foe (Confusion, Psybeam) or raising all of its stats (Silver Wind) which are both fantastic.

The trouble is that it largely can't do anything by itself. It desperately needed Poisonpowder in its learnset - Poison Sting is there, sure, but the chance of poison isn't guaranteed so you'll often wind up wasting three or four turns trying to get lucky while doing minimal damage. It, like Vespiquen, learns Toxic naturally, but much later - 38 isn't endgame by any stretch, but it could certainly have done with it before then. Light Screen is a crutch for other team members, and Protect is most useful in doubles (unless running down the clock on a poisoned foe in singles). It's the ultimate supporter, really. Very good as part of a varied team of six (and moreso in Emerald thanks to the large amount of double battles it can take part in) but not a mon for smaller parties or solo runs.

 

[ItsScaryCary]

mamoswine

 

[bdt2002]

mamoswine

Before anyone says anything about this post, I will step in and say this. Thick Fat with Ice/Ground typing and good HP is a really solid defensive combination, and I know Mamoswine’s Attack is where most of its appeal comes from in battle but if it wasn’t for a good defensive profile by Ice-Type standards Mamoswine wouldn’t be able to actually make full use of its power. It’s kind of like a Latias or Latios in that regard, where their strong defensive traits (and in their case, excellent Speed for the time) are what enables their threat potential. Bulkier, more defensive Mamoswine builds can work in both single and multiplayer, my personal favorite if I had to pick one probably being the bulky Stealth Rock setter.

 

[ItsScaryCary]

Before anyone says anything about this post, I will step in and say this. Thick Fat with Ice/Ground typing and good HP is a really solid defensive combination, and I know Mamoswine’s Attack is where most of its appeal comes from in battle but if it wasn’t for a good defensive profile by Ice-Type standards Mamoswine wouldn’t be able to actually make full use of its power. It’s kind of like a Latias or Latios in that regard, where their strong defensive traits (and in their case, excellent Speed for the time) are what enables their threat potential. Bulkier, more defensive Mamoswine builds can work in both single and multiplayer, my personal favorite if I had to pick one probably being the bulky Stealth Rock setter.

it has sneaky bulk

 

[DrumstickGaming]

Possibly a cliché example, but I feel like these three still aren’t quite as bad as they’re made out to be. I never said they were super strong in-game, but I can’t quite call them “the worst starter ever” or anything like that. Meganium once it’s fully evolved is actually quite difficult for most NPCs to take down, and while it won’t be doing as much damage as the other starters and prefers a slower pace of play, this evolution family rewards skill and knowledge of the game with a defensive backbone for your team to take advantage of. Maturing is realizing that it’s not Chikorita itself that is bad; it’s that Grass typing that’s holding it back. A hypothetical Water-Type Meganium may feel like it would be too similar to Suicune, I’ll admit, but a Fire-Type Meganium would almost certainly be one of the best defensive Pokémon in the entire game. Grass really is just that bad in Gens 2 and 3.

nah worst starter of all time is Yellow Pikachu, no exceptions

like at least Meganium and Serperior can use screens and stuff and have fundamentally good stats. Yellow Pikachu even with natural Thunderbolt does literally nothing. total trash that goes straight in dumpster

Vespiquen in DPP. Yes getting a female Combee is a pain, but Combee - unlike a lot of other weak Pokemon who need a little babying - isn't actually terrible to raise since Gust is a serviceable move for the early-game due to all the Bug- and Grass-type Pokemon in Eterna Forest/City. Odds are you'll catch one at least in the early teens, and it evolves early enough that it won't be a Combee for very long.

And despite her terrible typing, Vespiquen is pretty formidable. Power Gem at level 21 is incredibly good - it needs TMs or move tutors/reminders to be fantastic since it has to wait a bit too long for a decent Bug move, but Toxic and Heal Order do a lot for it. Base 102 defensive stats are crazy for something that evolves so early, and it makes Vespiquen a pretty darn good wall against a lot of what Sinnoh throws at you. Less so in Platinum, admittedly, where there's more Fire-types and opponents generally pack a bit more offensive coverage, but it's still a great option nonetheless.

Plus it's just incredibly fun to use. Kind of in the same vein as Magikarp and Feebas as a "this needs time investment to find and raise" sort of Pokemon, but neither as brutally strong as Gyarados gets or as grindingly difficult as Milotic is to evolve.



Hot take for RSE: Dustox. I've used this a few times and... well, I'd hardly call it one of the best defensive Pokemon ever, buuuut... it honestly ain't half bad for an in-game run. Well... with some caveats.

It has a lot of surprising positives. Shield Dust is an underrated ability: being immune to random flinch/paralysis is huge, especially considering it can tank a lot of neutral Special moves thanks to its decent bulk. And it's one of the better options against Brawly's gym thanks to Gust and Confusion. It gets a bunch of useful supportive options (Protect, Moonlight, Whirlwind, Light Screen, Flash) while the attacking moves it does learn either have a chance of confusing the foe (Confusion, Psybeam) or raising all of its stats (Silver Wind) which are both fantastic.

The trouble is that it largely can't do anything by itself. It desperately needed Poisonpowder in its learnset - Poison Sting is there, sure, but the chance of poison isn't guaranteed so you'll often wind up wasting three or four turns trying to get lucky while doing minimal damage. It, like Vespiquen, learns Toxic naturally, but much later - 38 isn't endgame by any stretch, but it could certainly have done with it before then. Light Screen is a crutch for other team members, and Protect is most useful in doubles (unless running down the clock on a poisoned foe in singles). It's the ultimate supporter, really. Very good as part of a varied team of six (and moreso in Emerald thanks to the large amount of double battles it can take part in) but not a mon for smaller parties or solo runs.

can confirm about Vespiquen being underrated, good Fantina counter with Toxic / Heal Order

Dustox sounds fascinating

 

[Scorpio]

IK Onix isn't the most well-regarded Pokemon for in-game, but when it's able to evolve into Steelix it can put in some work. I'm gonna use HGSS as an example since this is where I think it shines the most (plus it's the game I used one in):

Catching one in the lower level of Union Cave, you've immediately got an answer to Bugsy and your Rival's non-starter Pokemon, given their exclusively Physical attacking and its sky-high Defense. It's also a decent answer to That Miltank, able to sit and tank whatever it throws at Onix while using Screech to lower Miltank's defense before taking it out. From there, if you're willing to have a go at the Pokeathelon (which you should, it's actually good), you can get a Metal Coat without having to Thief from Magnemite. Upon evolving, Steelix gets respectable Attack and HP along with the much better Steel/Ground typing, which taking into account its even more bonkers Defense makes it even more impregnable on the Physical side, and from there it can continue to contribute up to the endgame.

 

[ScraftyIsTheBest]

Ferrothorn is a pretty overlooked choice for BW1 and BW2 playthroughs, but it's surprisingly good as a defensively oriented Pokemon. Unova has two notable spots with appealing team picks: one is the desert (Route 4+Desert Resort) where the real offensive powerhouses are in Krookodile, Darmanitan, and Scrafty, as well as other solid picks in Sigilyph and the fossils. The other is Chargestone Cave. Most people gravitate towards Galvantula who has Compound Eyes Thunder, or Eelektross and Klinklang who are good offensively, but Ferrothorn is an overlooked pick who I'd argue is just as fantastic and fun as Galvantula, Klinklang, and Eelektross are, despite skewing defensively. Grass/Steel is an incredible defensive type, and Ferrothorn has fantastic bulk on both sides as well as Iron Barbs to deal passive damage to physical attackers. But while Ferrothorn is slow and bulky, it can still dish out in return with Curse to bulk up and slow down, as well as a powerful STAB combo in Gyro Ball and Power Whip, with Ferro's Curse boosted Gyro Balls being hard hitting as hell. Payback is a bonus since Ferrothorn is nearly always gonna strike last.

It's definitely one of the better team picks in the Unova games that often gets overlooked because its design isn't that standout, but it's among a group in a dungeon with great team picks like Galvantula, Klinklang, and Eelektross and is just as good as them, and in some ways better. And it's also a great case of a defensive Pokemon who can be a strong in-game team pick. It doesn't have an immediately fun gimmick like the Desert mons (Krookodile and Scrafty steamrolling with Moxie or Darmanitan nuking everything with Sheer Force Flare Blitz) or its fellow Chargestone Cave denizens (Shift Gear Klinklang, Compound Eyes Thunder Galvantula), but it's got a fun schtick in its own right and one that makes use of a defensively oriented profile.

 

[DrumstickGaming]

IK Onix isn't the most well-regarded Pokemon for in-game, but when it's able to evolve into Steelix it can put in some work. I'm gonna use HGSS as an example since this is where I think it shines the most (plus it's the game I used one in):

Catching one in the lower level of Union Cave, you've immediately got an answer to Bugsy and your Rival's non-starter Pokemon, given their exclusively Physical attacking and its sky-high Defense. It's also a decent answer to That Miltank, able to sit and tank whatever it throws at Onix while using Screech to lower Miltank's defense before taking it out. From there, if you're willing to have a go at the Pokeathelon (which you should, it's actually good), you can get a Metal Coat without having to Thief from Magnemite. Upon evolving, Steelix gets respectable Attack and HP along with the much better Steel/Ground typing, which taking into account its even more bonkers Defense makes it even more impregnable on the Physical side, and from there it can continue to contribute up to the endgame.

I can confirm Steelix is pretty good in HGSS. Ice Fang on Lance is cool tech if you can dodge the special moves.
Onix/Steelix is actually kinda okay in DPPT too. While it has been some time since I've used it, it's obviously a decent Roark check, sits on Mars / Jupiter thanks to Screech, and has good type matchups post Wake.

What sets Steelix apart from Golem is that while you do give up Golem's high Attack and natural Earthquake (unfortunate) you get a much better defensive type that doesn't suffer any quad weaknesses. Onix/Steelix is imo a solid pick in most of the games that is only really hindered by trade stuff/Dig reliance outside TMs. Not half bad for a mon that started as a meme in the Kanto games.

To add some more substance to this post, Snorlax is a generally good pick in the games it's available in. Despite having bad Speed, a decent defensive type and amazing bulk lets Snorlax take a hit and keep on ticking. I recall it being really good in USUM in particular thanks to that game favoring bulky sweepers.

Scraggy is another solid defensive and somewhat offensive mon. Moxie makes up for its rather lacking Attack, good type, good matchups in the Unova games.

Gigalith is 100% an underrated Pokemon in BW1. Having 85/130/70 bulk at only level 25 is beyond absurd, so much so that despite the historically poor Rock typing Gigalith eats everything. It does lack in move diversity but the bulk is so good it kinda doesn't matter. Arguably in the top ten best picks for BW1. Don't bother in the sequel though, got power crept pretty badly. I'd say similar things about Conkeldurr minus the power creep bit, it's also really good.

 

[pe5e]

I feel like this needs some clarification of terminology.
Because calling something like Magnezone with its highest stat being special attack (namely 130, which is high even for usual offensively inclined in-game Pokemon) a defensive Pokemon sounds all kinds of wrong to me.

Here is how I would classify a defensive in-game Pokemon:

• Its highest stat needs to be a defensive stat (HP/Defense/Special Defence) aka it is "designed" to take hits.
• Its offenses can only be decent at most and it has to rely on chip damage from things like status or utility moves along with its weak normal attacks to take enemy Pokemon down slowly.
  If it has good offenses and just relies on normal attacking moves but can also take a couple hits well, then it is not a defensive Pokemon, it is a tank or bulky attacker (think Pokemon like Hariyama or Donphan, I would also classify Magnezone as a bulky attacker).

The second point is why pure defensive Pokemon are usually pretty bad for the main story of Pokemon games. They take to long to take enemy Pokemon out, they are a bit inconsisted sometimes due to more chances to get haxed and they don't really provide much of a benefit for these issues because you can take on the game with offensive Pokemon in much the same way, and usually even much better and more efficient.

Though there are a couple of defensive Pokemon who are actually decent, which is probably the most they can hope for in-game.
Here are a few that I think are solid enough:

• Tentacruel
• Umbreon
• Skarmory
• Dusclops
• Registeel
• Ferrothorn
• Florges
• Aegislash

Aegislash is probably a outlier because you could also say it is more of a tank but its really unique ability and stats make it function as a pure wall too to a degree.

I don't think I will name specific defensive Pokemon that are really bad because there are a ton but the usual hallmark is that they have a horrible defensive typing along with an overall low base stat total. So while these Pokemon are also clearly "designed" to be defensive, some of their attributes don't really allow them to even do that despite having a few good defensive traits. Magcargo could maybe be a poster child for this, though.

 

[DrumstickGaming]

I feel like this needs some clarification of terminology.
Because calling something like Magnezone with its highest stat being special attack (namely 130, which is high even for usual offensively inclined in-game Pokemon) a defensive Pokemon sounds all kinds of wrong to me.

Here is how I would classify a defensive in-game Pokemon:

• Its highest stat needs to be a defensive stat (HP/Defense/Special Defence) aka it is "designed" to take hits.
• Its offenses can only be decent at most and it has to rely on chip damage from things like status or utility moves along with its weak normal attacks to take enemy Pokemon down slowly.
  If it has good offenses and just relies on normal attacking moves but can also take a couple hits well, then it is not a defensive Pokemon, it is a tank or bulky attacker (think Pokemon like Hariyama or Donphan, I would also classify Magnezone as a bulky attacker).

The second point is why pure defensive Pokemon are usually pretty bad for the main story of Pokemon games. They take to long to take enemy Pokemon out, they are a bit inconsisted sometimes due to more chances to get haxed and they don't really provide much of a benefit for these issues because you can take on the game with offensive Pokemon in much the same way, and usually even much better and more efficient.

Though there are a couple of defensive Pokemon who are actually decent, which is probably the most they can hope for in-game.
Here are a few that I think are solid enough:

• Tentacruel
• Umbreon
• Skarmory
• Dusclops
• Registeel
• Ferrothorn
• Florges
• Aegislash

Aegislash is probably a outlier because you could also say it is more of a tank but its really unique ability and stats make it function as a pure wall too to a degree.

I don't think I will name specific defensive Pokemon that are really bad because there are a ton but the usual hallmark is that they have a horrible defensive typing along with an overall low base stat total. So while these Pokemon are also clearly "designed" to be defensive, some of their attributes don't really allow them to even do that despite having a few good defensive traits. Magcargo could maybe be a poster child for this, though.

Okay Magnezone being defensive might have been stretching it a little but I was looking at the defensive type because it literally has the most resistances of any Pokemon (at least as of Gen 5 I believe?)

As for pure defensive mons they are generally Just Not Good (TM). As for the ones you've mentioned:
-Tentacruel I've had success with but I find it hard to fully recommend, an Earthquake weakness on a rather average offensive Water type doesn't really bode well.
-Umbreon is just really hard to justify in general to me.
-Skarmory I've used in multiple games and it doesn't do much for me with the sole exception being Colosseum's endgame where it is borderline mandatory to get through the final battles.
-Dusclops I can't speak for too much.
-Never used Registeel.
-Ferrothorn I've used extensively and it's always been only alright in every game it appears. The defensive type is really nice but the offensive STABs are very mediocre so even with Curse it's hard to really attack back with. Far from a bad Pokemon but I can't truly say it justifies its teamslot.
-Florges would be cool in its debut game if it had actually good Fairy STAB moves before the end of time. Never used it.
-Aegislash is an outlier like you say, been forever since I've used it.

A good nomination for a lackluster defensive mon is Koffing in pretty much any appearance. Pure Poison with Levitate is attractive until you realize it just kinda sits there (coverage isn't a game changer off 85 Special Attack), the level 35 evolution level does not help either. Same with Yamask but for Ghost: similarly late evolution, meh coverage, not really standout bar Marshal where it's kind of good.

 

[pe5e]

As for pure defensive mons they are generally Just Not Good (TM). As for the ones you've mentioned:
-Tentacruel I've had success with but I find it hard to fully recommend, an Earthquake weakness on a rather average offensive Water type doesn't really bode well.
-Umbreon is just really hard to justify in general to me.
-Skarmory I've used in multiple games and it doesn't do much for me with the sole exception being Colosseum's endgame where it is borderline mandatory to get through the final battles.
-Dusclops I can't speak for too much.
-Never used Registeel.
-Ferrothorn I've used extensively and it's always been only alright in every game it appears. The defensive type is really nice but the offensive STABs are very mediocre so even with Curse it's hard to really attack back with. Far from a bad Pokemon but I can't truly say it justifies its teamslot.
-Florges would be cool in its debut game if it had actually good Fairy STAB moves before the end of time. Never used it.
-Aegislash is an outlier like you say, been forever since I've used it.

Tentacruel is mostly a specially defensive Pokemon, it is not taking physical hits that well. The Ground weakness is annoying but especially in early gens where special Ground moves didn't exist, Water / Poison is actually a fantastic defensive typing against special attackers, which it can take on very well due to its good movepool and Water typing. And the good speed stat is kind of rare among defensive Pokemon.
Umbreon, Skarmory and Dusclops are all very similar, in that they just sit there and take hits. But among Pokemon that just do that, they do it rather well as they are very hard to kill for most things. Not dying is not that impressive of a feat for in-game but still you can play that way an do fine with such Pokemon. But as I said fine is the upper threshold for such pure defensive Pokemon.
Ferrothorn, Florges and Aegislash just have really, REALLY good defensive typings and stats, so they serve a defensive role well, even if they just slowly chip Pokemon down with normal attacks.

A good nomination for a lackluster defensive mon is Koffing in pretty much any appearance. Pure Poison with Levitate is attractive until you realize it just kinda sits there (coverage isn't a game changer off 85 Special Attack), the level 35 evolution level does not help either. Same with Yamask but for Ghost: similarly late evolution, meh coverage, not really standout bar Marshal where it's kind of good.

As far as gens 2-4 go, Koffing is not THAT bad. It has decent defenses and mostly talkes neutral hits. It has good coverage and also solid utility moves. Nothing more than an average Pokemon overall but not as bad as some of its issues would imply imo.
There are many defensive looking Pokemon that perform worse (like Lileep who I hate with a passion).

 

[DrumstickGaming]

There are many defensive looking Pokemon that perform worse (like Lileep who I hate with a passion).

It's such a shame too because Cradily is really awesome in competitive but so passive there's no reason to use it in-game.

Believe it or not, I found that Lopunny is super good in Black and White 2. Which is odd because you'd never expect it to be.

If you have any defensive Pokemon you think are utterly terrible, feel free to humorously rant about them.

 

[Eeveeto]

Many have been mentioned, I will add one: Dewgong:
-Solid bulk despite not having a single Stats above 100.
-Thick Fat adds an extra resistance despite the Ice typing.
-Good STAB combination that make its Ice Beam as strong as offensive Water ones.
-Learns Rest (most important in-game TM by far) by level up. On Gens without multiple use TMs or in games in which Rest comes late, this is a very useful asset if you can get a Dewgong.
-Lastly, since DPP it learns Encore by level up. Encore in-game is broken. Any dumb move by AI is exploited and you can switch to the apropiate counter. Good moves are exploited too, Dewgong tanks a Tbolt, Encores it and you can switch the Ground in.

For all these reasons, Dewgong is one of the best Mons to use in Nuzlockes. Lapras or Cloyster are not such an upgrades. Unfortunately, Walrein is, having superior Stats, same typing and same movepool, but often Dewgong and Walrein are not in the same games.

 

[Hugin]

I'm going to call almost every grass-type starter after Gen 2 a terrible defensive pokemon. So, grass is an awful offensive type, being NVE against 7 types. But grass gets a bunch of good support moves, like Leech Seed and status-inducing moves. AND YET their movepools are terrible for support. I've said it before, but it's like GF decided that Meganium being disliked/weak meant that every grass starter should be either a fast attacker(Sceptile, Serperior, Meowscarada), a bulky attacker(Chesnaught, Rillaboom), or suck(Decidueye). Torterra is the only one who gets a useable support/stall movepool*, and it also gets ground coverage and set-up moves so it's more fun to use it as a sweeper. A far cry from Venusaur in gen 1 with Leech Seed from almost the beginning to teach kids how to chip down unbeatable targets.

*Leech Seed, Synthesis, Sandstorm, Stealth Rock. And even some of those are stretching/TMs.