First time posting VRs. Taking time to think harder about the individual Pokémon in the metagame is surprisingly challenging, considering much of what constitutes them has already been said a million times over. Anyway, let's get into it:
S Tier:
1st –
Tyranitar:
I mean, he’s the guy you think of when you think of ADV for a reason: Cutting into most of the tier’s recovery with Sand Stream, having so much flexibility with sets and moves within sets is huge, what can I say that hasn’t been said before?
2nd –
Skarmory:
Yeah, absurd physical bulk, good enough special bulk when invested, Spikes, Roar, Drill Peck and more, definitely not as flexible as most other mons, but it’s amazing at what it does, Spikes is lowkey overpowered.
3rd –
Blissey:
This is slightly controversial, but I fully believe that Blissey’s capability to wall almost all of the special side of ADV while being so bulky health-wise that it can serve as an emergency physical check with Thunder wave/Counter is insane, absurdly polarizing and powerful pokemon, all while having surprising flexibility on moves: Need to heal your teammates? Wish. Need extra help vs Calm Minders? Calm Mind youself. Want to lure physical threats and eliminate them? Counter. Want to be super obnoxious? Thunder Wave. You get the point. S tier for me.
A Tier:
4th –
Swampert:
I believe Swampert’s physical walling, paired with it’s threat (if you ever loaded a team weak into offwaters into an Offpert, you’ll know what I’m talking about) + the possibility of Endpert makes it better than Metagross, though not by much. Also, it’s ground typing allows it to check fires and electrics (of course, it depends on what Hidden Power they’re packing). Great Pokémon with a goated typing, nearing S tier IMO.
5th –
Metagross:
A bit low compared to most other people. I think Metagross has several roles it can fullfil, but it does feel like it always wants a bit more. Agilmeta kinda hates having to choose between Lefties, which means being prone to paralysis/burn, and Lum Berry, which cuts into it’s survivability quite a bit, and also between Explosion, helping break for his team, and Rock Slide, which helps hit the flying mons such as Zap and Molt. Bulky Meta hates how it’s weak to ground moves. CBMeta can be insanely threatening, but it’s worn down with ease and can thud into certain things, not to speak of how Houdini can be inconsistent (I almost always pair CBMeta with Spin). Mixmeta is pretty good but often feels like it lacks a bit of the punch that Agilmeta/CBMeta has. Don't get me wrong, it's still an amazing Pokémon, but I feel it lacks the sauce to break into top 4.
6th -
Zapdos:
Thunderbolt's strongest soldier, that thing can fire off those like no one else. Spikes immunity and great resistances help it hit the field a lot, Hidden Power choices mean you can snipe either Swampert or Salamence/Flygon (beware of being outsped, though). Good flexibility in the last 2/3 moves, between Toxic, Thunder Wave, Light Screen, Rain Dance, Agility, Baton Pass, Substitute, Rest, Drill Peck, Roar and more things I'm probably forgetting about. Loves being paired with Spikes as there's nothing other than Claydol and Flygon, which hates Hidden Power Ice/Toxic, that is immune to both Thunderbolt and Spikes, meanwhile, the momentum it generates for CMPass with SubPass is massive. Almost dropped it to 7th after the SpeedPass ban, but I think Zapdos is still a massive threat.
7th -
Salamence:
Speaking of flexibility, here's the pokemon that can threaten just about the whole metagame until you know what it's running. Can't speak much about WishMence since I used it like once or twice only, but MixMence forces so much damage with the overall neutral, powerful click that is Dragon Claw. Dragon Dance is also a massive threat in endgames when defensive pieces are chipped. Choice Band feels way worse, but it has it's place and also has to be respected. Of course, spikes immunity with intimidate and decent bulk is also always appreciated, notably pairing well with Metagross as physical checks.
8th -
Jirachi:
Same typing as Metagross, 100 base stats across the board, Calm Mind and Serene Grace, this thing is insanely scary. DefRachi patches up the Aero matchup for so many teams while being obnoxious to face if you don't have a Dugtrio (even then, you fear paralysis), Calm Mind can choose between a myriad of coverage moves and Substitute, MixRachi can click buttons super easily, lure and severely hurt pokemon such as Tyranitar, amazing Pokémon with the potential to steal games away with Serene Grace freezes, burns and paralysis.
9th -
Gengar:
Best Ghost type by a mile, pretty good spinblocker, enough stats to hit just the right ranges and live the right moves you need it to, spreads Wisps like nobody's business (75% of the time), great Blissey breaker alongside spikes, big threat until you know what moves it's running and even after that it can still be terrifying, not to mention how Normal, Fighting and Ground immunity is amazing. Having a sleugh of utility options in Wisp, Taunt, Hypnosis, Destiny Bond, Snatch and even the odd Substitute certainly helps it a ton, amazing Pokémon with a big skill ceiling.
10th -
Suicune:
People seem a bit down on Suicune, but I'm still a believer. Pure Water typing, while not perfect for it, is great for checking Rocks and Grounds, has the ability to Pressure stall a bunch of moves (Giga Drain kinda sucks into it if you're not careful), very powerful STABs, Ice coverage, the odd Hidden Power coverage in Grass/Electric, access to Substitute, Rest, Roar and Sleep Talk, not to mention it's main thing: Using it's bulk to get Calm Minds going.
11th -
Celebi:
Yet another mon with huuuuge flexibility, but it will always have considerable drawbacks. Leech Seed is an amazing move, of course, and Calm Minds are a good way to both be a threat and pass the boosts to something else so they also become a threat, good defensive typing that allows it to check Zapdos decently well, however, it suffers a bit of 4mss, since it loves Leech Seed, but also wants Recover to help it be a long-term check to Zapdos, but it also wants HP Fire to not let Skarmory spike for free, and it wants Psychic for STAB, Giga Drain/Hidden Power Grass for secondary stab and hitting Suicune/Swampert/Dugtrio is also great, Calm Mind also helps it be more threatening outside of super effective moves... You get the point, good mon but it always feels like it wants a bit more.
12th -
Claydol:
Checks all, counters none. Best spinner in the tier by a good margin, turns out spinning is way easier when you're immune to Spikes and Sandstorm, good check to Tyranitar and Metagross due to it's STAB Earthquake. STAB Psychic also allows it to hit Gengar trying to spinblock, which is often a way for teams to lure Gengar in and kill it. Rapid Spin needs no introduction and neither does Explosion. Having the options in Shadow Ball to hit all Ghosts, Rock Slide to hit Flyers and better check Zapdos and Refresh so fatter teams can play long term with it with more ease, amazing toolkit and typing on an underwhelming but usable statline.
13th -
Dugtrio:
Very polarizing mon, with some people (though it's a minority) wanting it gone. Trapping is, of course, massive, and can be used by skillful team builders and players to create great gamestates. Thankfully, I don't think that it enables anything overpowered, because I love Dug's presence in the metagame. Great mon, but it's kinda fragile, usually requires chip before trapping and/or to switch in for free (whether it be after something else faints or with a Sub BP) and can have it's Eq lock abused by mons such as SubBP Zap, Aero and DDMence.
14th -
Aerodactyl:
Speaking of Aero, highest speed tier alongside Jolteon in OU (no, Jask and Electrode don't count), powerful banded DEdges hit insanely hard, while having Earthquake for any Steels not named Skarmory. Rock Slide singlehandedly inspiring the phrase "If there's an Aero, there's a way", HP Flying also being a pretty good neutral click while HP Fighting helps you be more consistent into TTar and HP Bug allows you to spinblock Claydol and Starmie if you get the switch right. Not a huge fan of SubLiechi, but it has it's uses too.
15th -
Snorlax:
Big threat, great special check for more offensive teams, spreading paralysis with Body Slam is great, but it's very prone to being worn down (and Rest usually turns you into a sitting duck), also being terrified of Wisp. I do have to say that Curse Double-Edge is a pretty neat way to compress the spammable STAB power of Return with the Skarm-threatening power of Self-Destruct (shoutout to Mielke)
16th -
Charizard:
Feels very similar to MixMence, but it hits harder with Fire Blast and has Blaze to hit even harder while having Focus Punch/Beat Up for Blissey. Great check for Metagross too, but the lack of Intimidate and overall lower bulk means it's worse at checking most other things defensively. Still, I think it's way too good to be B tier (also, another Pokémon that enjoys Spikes quite a bit, especially to break Suicune with HP Grass on the switch/behind a Sub)
B Tier:
17th -
Starmie:
Super fast Pokémon with BoltBeam coverage, Rapid Spin, STAB Pumps, Recover, Thunder Wave, Natural Cure and decent bulk, only issue is how it thuds into special walls and is weak to Spikes if it doesn't have Recover (which it often doesn't), not much more to be said.
18th -
Magneton:
Traps the second best Pokémon in the tier while also trapping CBMeta, trapping Forretress and acting as a Gengar/Mono Water check, spreading paralysis with Thunder Wave is also very neat. Great at enabling physoff and faster spikes-weak structures in general, not much else to be said.
19th -
Milotic:
Milotic often feels impenetrable, not having any 4x weaknesses nor any physical weaknesses while also having Refresh to stop it from being worn down by Toxic, Recover to heal itself up, Toxic to threaten a lot of things out, Hypnosis to get turns for it's teammates, Ice Beam to snipe Salamence and other flyers trying to come into a Surf and, of course, Surf itself. However, it suffers a lot from it's passivity, often being seen as a "hax magnet" due to how long it stays on the field without threatening enough in return.
20th -
Forretress:
Has great tools too in Rapid Spin, Spikes, Explosion, Counter, Earthquake for sniping Magnetons, Zap Cannon and Hidden Power Bug while having a pretty good typing, however, said typing does give it a big 4x weakness to Fire. It is also pretty liable to getting worn down by Spikes and stray attacks such as Skarmory Drill Peck and, much like Milo, feels like a "hax magnet" due to it's passivity.
21st -
Flygon:
Rock type check that is immune to Ground/Spikes while being faster than Swampert and having Fire coverage, however, it also has lower bulk (80/80/80 vs 100/90/90) and less offensive firepower (100/80 vs 110/85) and lacking the Water type, usually the rock resist for Superman teams, but also fits well as a faster, more offensive Rock Check. Not bad at all, just niche and suffers from having to compete with Swampert.
22nd -
Heracross:
Extremely threatening Pokémon with the potential to end games on the spot if well-positioned. Why did I place it 22nd then? Well, it usually will lack pretty significant tools (If Salac, then it's easily worn down. If Lefties, it's easily outsped. Etc), it hates relying on 85% accurate Megahorn and 90% accurate Rock Slide and, most important of all, it's not easily put on the field, having bad bulk and resisting Bug, which is a rare type which often isn't clicked into Hera teams, Fighting, which is also rare outside of Focus Punch which will still chunk quite a lot, Grass, which is another rare-ish attacking type, Dark, another rare attacking type, and Ground, it's most relevant resistance, often clicked by mons which can also click other moves that threaten Hera a lot. If you struggle to get the Pokémon on the field, it'll get less turns threatening the opponent. However, if you can get it to work, as said, it's absurdly powerful.
23rd -
Moltres:
Recently on a downwards trend in the eyes of a lot of the community and for good reason. Sure, it hits harder than Charizard (barring Blaze-boosted fire moves), has access to Will-o-Wisp, which is huge, and access to Roar too, however, it struggles to click Will-o-Wisp into many of the physical threats it wants to hit with it/Roar in the face of setup sweepers, not to mention how much it thuds in the face of Blissey, while also having base 90 speed, leaving it slower than the plethora of base 100s in the tier (and, notably, most Tyranitars at +1 speed). However, I still respect it's threat enough to have it 23rd.
24th -
Jolteon:
Shares it's amazing speed tier with Aerodactyl, great Zapdos check for faster-paced teams, hits hard enough with it's Thunderbolts to threaten stuff, has, of course, HP Grass/Ice to hit grounds, spreads Thunder Wave quite well, has BP to keep up the pressure, SubPass is a threat too, having Roar and Wish are also cool. However, it's very frail and can't heal outside of Wish (takes 2 turns) and coming into electric moves (If it's unrevealed, it'll take, at most, Spikes damage anyway, and if it's revealed then the opponent will be disincentivized to click those), so it can be worn down (especially if it's passing subs) and HATES being paralyzed/outsped (+2 Meta/Ttar and +1 Mence, mainly). Sadly, it also hates facing Claydol, a very common Pokémon in the tier.
C Tier:
25th -
Raikou:
Not as fast as Jolt and the like but still sits at a great speed tier, has slightly more powerful Thunderbolts than Jolteon but with the threat of Calm Minds behind it too. Can, as always, pack HP coverage and, notably, also Crunch (helps hit Claydol, for one), while being able to run other moves such as Roar and Substitute too, scary cleaner that can end up struggling if it has the wrong HP choice or if it's facing a Dugtrio.
26th-
Medicham:
I'll say that I was higher on it a bit before it rose to OU, however, it's a bit too prediction-reliant and frail to really be too much higher. I still think it's worthy of OU, as Huge Power Fighting STAB with alright speed is great, but it feels like it's almost only usable in the lead slot.
27th-
Cloyster:
Spiker that doesn't get trapped by Mag, usually also gets to either Spin or Boom (rarely both) in a game and has actual offensive presence with Surf/Ice Beam, not bad but has terrible special bulk and quite a few physical weaknesses, which may make it hard to get it onto the field. Not a bad mon though, just usually fits offensive teams better.
28th -
Registeel:
Mono Steel with 80/150/150 bulk, access to SToss, TWave, Boom, Earthquake and more, great way to have a special check that also checks a lot of physical Pokémon when your team needs it (like if you're running EndPert), definitely worthy of OU IMO.
29th -
Breloom:
I was once a hater and, to be honest, still am, but less so. Turns out 100% accurate sleep + STAB Focus Punch off of 130 base attack is kind of powerful! However, it's incredibly frail and can get goobed by good prediction/Lum users while lacking coverage outside of HP and Rock Slide.
30th -
Regirock:
Mono Rock with 80/200!!!!/100 bulk and 100 attack means you'll be tanking physical hits, even super effective ones, like nobody's business. Great as a "sandless Ttar" for sandless teams. Threatens Boom really well while matching up with Ttar itself quite well due to Superpower, just an overall pretty cool Mon that's liable to being chipped/statused. I'd say it's worthy of OU but I'm not sure, this is definitely the last one in the rankings I'd consider for OU though.
31st -
Regice:
Unduggable special check for those who cannot or don't want to fit Snorlax for one reason or another. Powerful Ice STAB with Tbolt coverage is really good, of course, notably being very good into Superman archetypes, but it's too easy to wear down while thudding into too many Pokémon for it to be OU.
32nd -
Jynx:
Starts the game off with a sleep (75% of the time, lead Lum notwithstanding) and by getting Calm Minds going. Usually either wins or loses really fast, powerful but unreliable Pokémon. Notably, can also lure and Perishtrap Blissey for special offense.
33rd -
Vaporeon:
I was originally going to rank it a bit higher, but I think the ban of speedpass hurt it a bit. Can pass 101 Subs, pass Wishes, fire off powerful Hydro Pumps (notably, more powerful than Suicune's at neutral), has Roar and Ice Beam too, still an alright mon, especially with Water Absorb owning monocune/Refpert (when paired with Sub).
34th -
Gyarados:
Yes, I think Gyarados is a fraud. Harder to get going than Salamence for less firepower, gets owned by any stray Electrical hit and, sometimes, even Rock hit. Has to sacrifice it's already not great physical power (considering the lack of good STAB) if it wants to outspeed Jolteon and Aerodactyl at +1. Thuds hard into Skarmory (and don't tell me to run Taunt HP Rock. 252 Atk Gyarados Hidden Power Rock vs. 252 HP / 0 Def Skarmory: 56-66 (16.7 - 19.7%) -- possible 7HKO // 0 Atk Skarmory Drill Peck vs. 68 HP / 0 Def 30 IVs Gyarados: 89-105 (25.5 - 30.1%) -- 0.4% chance to 4HKO after Leftovers recovery). I never respect it in the builder and IDR ever being punished by it. His DD Rest sets may have potential and it does check Fighters quite well, but I don't think it has a place among the OU Pokémon.
35th -
Machamp:
Bulky fighter that has access to Low Kick and Guts, alright Rock/Normal check, though it's easily worn down. Very similar to Hariyama but it gets the edge for me due to having slightly higher attack, Low Kick and better defenses. Bulk Up is also scary, of course
36th -
Hariyama:
Compared to Machamp, it has to use Cross Chop over Low Kick, meaning lower accuracy, but it also gets access to Thick Fat if it wants to ditch Guts, has way more HP (switches into SToss better) and, of course, Knock Off, the best move that barely anything gets in ADV.
37th -
Kingdra:
Is the main face of Rain Offense, hits absurdly hard on Rain with STAB and gets outsped by nothing. Outside of Rain, though, Kingdra's a bum. Heavily stallable with Blissey/Protect. Not having any weaknesses outside of Dragon is neat though!
38th -
Misdreavus:
Ground immune Ghost that isn't weak to Psychic! Neat! Really good in that one ABR Superman, mediocre everywhere else.
Won't talk about anything below C (I already lack experience in using some of the lower C stuff, let alone D and E, besides, the post would get even longer), just wanted to say I originally also had Smeargle, Ninjask and Marowak there before the Speedpass ban.