S Rank
Combusken - Speed Boost lets Combusken be one of the most threatening mons in the tier as it can run a special attacking or SD set to great effect, it doesn't have too many counters or checks as well.
Doublade - Great typing and bulk, allows him to be very splashable and check a bunch of threats, and can also be very threatening offensively.
Porygon2 - Bulky and powerful, can run a variety of sets and pull them off, overall a very dangerous mon.
A Rank
A+
Dusclops - The bulkiest mon in Middle Cup overall, letting it check many threats as well as being an offensive threat with an offensive set. But it does have some flaws, such as being passive if it's defensive and having no reliable recovery.
Fletchinder - Awesome mon due to having priority Acrobatics, letting it be a great revenge killer and even a sweeper thanks to Swords Dance. It also can run a bulky utility set to good effect thanks to walling Fighting and Grass-types. The Stealth Rock weakness hurts it, though.
Fraxure - Stupidly strong sweeper with Dragon Dance and 117 Base Attack and good coverage, only one good counter in Doublade if it runs Poison Jab. Does sometimes have problems setting up and is checked by priority.
Golbat - Probably the best Defogger in MC thanks to walling Roselia and winning against some other hazard setters, like Monferno. It also has great utility in walling Grass-types and Fighting-types, and also has an offensive presence with Brave Bird and can also run a cool Nasty Plot set.
Gurdurr - The premier Fighting-type, with great bulk and a good boosting move in Bulk Up, as well as being a status absorber with Guts and having semi-recovery in Drain Punch and priority in Mach Punch. Knock Off is also great, and you can also run Poison Jab if Fairies are a problem. Great mon overall.
Monferno - Great mon as it can run a variety of sets, like AoA, Stealth Rock, Nasty Plot, and Swords Dance. Receives competition from Busken, but it's unique options let it stand out.
Rhydon - One of the most splashable mons thanks to it's gigantic physical bulk and good typing, as well as Stealth Rock and a good offensive presence. It can also run a very threatening Swords Dance or Double Dance set to goof effect, only problem is the typing letting it be threatened by Grass and Water-types, as well as being lured by stuff like Giga Drain Golbat easily.
Roselia - The best Grass-type in the tier, with good bulk overall and being one of the best hazard setters by winning against most of the Defoggers in Middle Cup. Can check a myriad of threats as well, as well as being an offensive threat with it's good Special Attack.
Sliggoo - A great offensive and defensive threat, with an awesome typing and abilities letting it wall many threats. Can be a great help to many teams, but the low physical defense hurts it a bit.
A
Croconaw - Scary sweeper or wallbreaker with Sheer Force + LO with good boosting moves in DD or SD, also has decent enough coverage as well as Aqua Jet. Be sure to look out for Croconaw.
Electabuzz - The premier Electric-type, with the highest unboosted Speed Stat in MC tied with Kadabra, letting it threaten a lot of teams with his power and coverage. Walled by some threats, though, such as Sliggoo.
Haunter - Great offensive threat with good Speed and can run a variety of sets, like Scarf, AoA, or even a SubSplit or SubWisp set. It doesn't have that good of bulk however, and Shadow Sneak really hurts it.
Kadabra - Amazing Special Attack stat along with a very high Speed stat lets Kadabra be very threatening to many teams, the lack of bulk and vulnerability to priority hurts it though.
Magmar - Very powerful Fire-type with great Speed as well, receives some competition, but it still has a very good niche in it's power and Speed.
Piloswine - Great mon with good typing and a great ability in Thick Fat, reliable Stealth Rock setter, can also be a jerk to offensive builds with Ice Shard.
Prinplup - Great Water type that is also a good Defogger and also can set up Stealth Rocks. It can also run a more offensive set that can threaten a good amount of stuff.
Servine - Threatening sweeper with Contrary Leaf Storm, but it doesn't have the coverage or sometimes the Speed to pull it off. A scary threat definitely, but it's walled by too much overall to be A+.
Togetic - Great check to a lot of things, can WishPass okayly, also can Baton Pass Nasty Plot boosts or run a more offensive Nasty Plot set to good effect as well. It's also a decent Defogger despite being weak to SR.
Zweilous - Terrifying wallbreaker with Hustle, and also has good resistances so it can run a RestTalk set nicely as well. It's pretty suspectible to Fairies and is weak to Fighting however, so not always the best choice.
A-
Gabite - Rough Skin is a really cool ability, and Gabite can make good use of it, detering physical attackers nicely while also setting up Rocks or attacking. Sadly can't learn SD, which is a shame as it can't really break through walls that well.
Gothorita - Shadow Tag's a bitch, as Goth can trap and revenge kill a lot of threats with Choice Scarf, or set up on them with Calm Mind, or be a good overall offensive threat with Specs.
Grovyle - Fast and powerful, letting it be a very big threat to offensive teams. SD sets are also really good sweepers, it is frail though.
Krokorok - Probably could rise to A, it's so good. Ground/Dark is a great offensive typing while also being a good offensive Rocker and having two great abilities letting it be a good cleaner or check to some physical attackers.
Magneton - Traps Steel types and also has Electric typing to beat Water types, Choice Specs hits like a truck, and it can also run Choice Scarf to good effect as well.
Marshtomp - Has a great Water/Ground typing and Stealth Rock, letting it be a good defensive mon overall, but the Grass weakness and overall passiveness hurts it.
Metang - The only relevant Steel-type that gets Stealth Rock, and it also has some nice moves like Ice Punch, Zen Headbutt, and Earthquake to give it a niche over other Steels, still a bit shafted by Doublade though.
Quilladin - May receive competition from Roselia, but Bulletproof and better physical bulk lets it be a very good Spiker on some builds. Unique moves like Zen Headbutt and Drain Punch also lets Quilladin be a good lure as well.
Vibrava - Really underrated Defogger, can check a lot of threats while also having reliable recovery in Roost. Offensive Defogger Vibrava is also really cool, as LO Draco Meteor hits like a truck. Does get checked by some stuff like Piloswine though.
B Rank
B+
Duosion - Probably should drop to B, but let's give it a chance. It's OTR set is very frightening for offense to handle with Duosion's powerful 125 Special Attack, and Calm Mind isn't bad either. Kadabra and Gothorita overshadow it mostly, though.
Clefairy - Great ability in Magic Guard along with decent bulk lets it carve out a niche over Togetic as a Fairy-type, sadly it doesn't have Unaware to stop set-up sweepers and it needs boosts to be threatening.
Gloom - Roselia overshadows it sadly, but Gloom still has a niche in having more physical defense and being able to Sun sweep.
Lombre - Pretty dangerous Rain sweeper with good STABs and coverage overall, sometimes lacks a little power though, Fast SubSeed is also a really fun set that can fuck over walls nicely, try it out sometime.
Seadra - Very scary Rain Dance sweeper even without Swift Swim thanks to a good 85 Speed and awesome 95 Special Attack lets it be a wallbreaker under Rain also. Sort of frail on the special side, though.
Staravia - Crazy powerful wallbreaker with Reckless and it's STABs, it can also run mixed with HP Water to lure in Rhydon as well. Very good with Fletch as BirdSpam.
Vigoroth - GreTat bulky sweeper with Bulk Up, and it also beats stall really nicely. But it can get walled by Ghosts or Steels if you don't run the coverage moves to beat them, so it needs some support to work.
B
Dragonair - Really nice Dragon Dancer with access to neatmoves like ESpeed and Fire Blast to roast Steel type switchins. The mixed set with Draco Meteor is a monstorous wallbreaker as well.
Eelektrik - Has a niche over other Electrics in Levitate and a great movepool with gems like Knock Off and Giga Drain. Sadly it's pretty slow, which means it has a bad time against offense.
Klang - Decent sweeper with Shift Gear and good bulk to set up on Fairy types, but gets walled by a lot of things, like bulky Water-types and Steel-types.
Lairon - decent Rocker that has a niche over Rhydon in Steel typing and Rock Head Head Smash, can also run a nice Rock Polish set or a Choice Band set. Sorta niche though.
Lampent - It doesn't have that bad of a typing, as it can wall stuff like Combusken and Monferno lacking Rock coverage thanks to Flash Fire, and it's OTR set can be a great pain for offense. SubCM sets destroy stall pretty nicely once Rhydon is gone. It is pretty slow though, and it faces competitoon as well. Overall a pretty cool mon indeed.
Pikachu - Powerful with a good priority move in Extreme Speed, but it's insanely frail and gets walled by some mons if it's lacking the right coverage move.
Sealeo - Nice Ice STAB moves and moves like Encore give it a niche over the other Waters, but it has a lot of weaknesses that make it pretty niche in general.
B-
Grotle - has a niche in Stealth Rock and being a neat sweeper with Curse, but faces competition from Roselia as a Grass-type hazard setter and is quite slow.
Ivysaur Another good sun sweeper, but misses out on Weather Ball in exchange for more bulk. Overall pretty good, but faces competition from Gloom and the other Sun sweepers.
Kirlia - Faces massive competiton from the other Psychic types, but it has a secondary Fairy typing that lets it carve out a niche along with unique moves such as Healing Wish, but it's slow and frail.
Marill - Huge Power + amazing typing makes Marill a great check to many top threats and a wallbreaker all in one slot. Sadly it is very slow, meaning it relies on Aqua Jet against offensive teams and it doesn't have much bulk.
Pignite - Probably could rise up a couple of ranks, I haven't really tested it out. It does have nice bulk and a nice enough typing coupled with good moves like Head Smash and Flare Blitz. But I don't see too much of a reason to use it over the other Fire-types.
Shelgon - Quite bulky, maing it a nice bulky sweeper with Dragon Dance, sadly it faces competition from the other Dragon-types. Rock Head Double-Edge is nice coverage though.
Skiploom - A great support mon for sweepers with moves such as Sleep Powder and Memento, as well as U-Turn to gain momentum. Not too powerful tho, and doesn't do much outside of supporting.
Swadloon - Has Sticky Web, whch is awesome, Magic coat is also really good to bounce back taunts, Defogs, other hazards, etc. It sadly doesn't have a very good typing and is pretty predictable.
Weepinbell - Great sweeper in Sun with moves like Growth and Weather Ball. Is pretty frail though.
Whirlipede - Really nice for offensive teams because of it's acccess to Toxic Spikes and Spikes, lettng it function as an effective lead. Sadly it doesn't have much options other than the lead set, and it faces competitoon from other hazard setters.
C Rank
C+
Braixen - A powerful special attacking Fire-type with Psychic coverage as well. Sadly it faces competition from the other Fire-types, especailly Combusken and Monferno.
Charmeleon - Amazing Sun wallbreaker thanks to Solar Power booosting it's Speciial Attack to monstorous levels, but faces competitoon from other Fire-types and is pretty niche in it's role.
Luxio - A cool Electric type with two good abilities in Intimidate and Guts, but it doesn't have great coverage and faces competition from other Electrics in general.
Nidorino - Hustle makes Nidorino pretty powerful , and it has the right physical coverage along with a boosting move in Hone Claws to work, but it's frail and has competition with other physical sweepers.
Nuzleaf - Another Sun sweeper, but it does lack some power sometimes and faces competition.
Pidgeotto - Although it only has 50 Special Attack, access to good moves such as Hurricane and Heat Wave give it a good niche as a special attacking Flying-type, and Work Up lets it beat defensive teams as well. Sadly, it's piss-poor defenses hurt it, and it faces competition from the other Flyers.
Pupitar - Has a niche in being a cool Dragon Dance sweeper with STAB EdgeQuake coverage, but has a bit less power than other sweepers and faces competition from Rhydon.
Vanillish - One of the two relevant Ice-types in Middle Cup, and it's powerful as well. Sadly it can't learn Freeze-Dry to break Water-types, and it sort of slow without a boost as well.
Wartortle - THE ONLY RAPID SPINNER!!!! That's nice and all, but it faces competition from Prinplup and other bulky Waters, and doesn't have much of a movepool to make up for it.
C
Dewott - Has cool stuff like Swords Dance that give it a niche over other Water-types, but the lack of coverage and overall competition make it a mostly inferior choice.
Herdier - Scrappy with Choice Band makes Herdier a great wallbreaker, and paired with Magneton for trapping Steels it can do a great amount of damage, but it does have a lot of competition.
Loudred - Has good mixed attacking stats along with a grear movepool with stuff like Fire Blast and Ice Beamm, but it faces competitipon from the Noraml-types, and it is pretty slow for an offensive mon.
Palpitoad - Has potential in Water Absorb and Swift Swim sadly it can't even learn Earthquake and is suspectible to Toxic.
C-
Flaaffy - Is pretty bulky and has some cool options like Focus Punch, but it's usually a bad choice because of the competititon it faces.
Floette - Amost entirely outclassed by the other Fairies, as even Togetic can pass bigger Wishes. Does have a niche in being offensive and having stuff like Calm Mind (Although Clefairy already gets it)
Nidorina - Only niche is in Toxic Spikes, but even Whirlipede gets it. Sort of cool though.
Poliwhirl - Water Absorb and Swift Swim along with gems like Belly Drum and Focus Punch give Poliwhirl a small niche, but one again, the competition it faces make it a mostly inferior choice.
Quilava - Has a niche in Erption and moves like Extrasensory, but with hazards being so good and the competition, Quilava isn't very good.
D Rank
D
Bayleef - Screens is the only thing Bayleef has over other Grassers, but even then it dosn't have much of a niche.
Boldore - Only niche is in Cutap Berry leading with Stealth Rock and Explosion, even then it faces competiton from Rhydon and other Rockers.
Jigglypuff - Outclassed by Clefairy as a Fairy type Stealth Rock setter. Nuff said.
Machoke - Outclassed by Gurdurr almost entirely except for No Guard DynamicPunch, whcih even then doesn't give Machoke much of a niche.
Tranquill - Bad mon is bad.