Dropping a few thoughts here given the discussion that's come up in the past few weeks:
Mega Gyarados from B+ to B: VERY STRONGLY Disagree
Yeah, I just can't see this thing being two subranks below vanilla Gyarados and I can't see vanilla Gyarados not being A- at worst (or at best tbh). I'd argue that it sharing a ranking with Mega Swampert isn't entirely unreasonable considering what archetypes these particular Megas fit on as well as what precisely they function as: powerful sweepers that fit on offensively-oriented teams that can dismantle walls in their own unique ways. While Mega Swampert can brute-force its way past incredibly bulky stuff due to its crazy Rain-boosted Waterfalls and solid coverage otherwise, Mega Gyarados takes more of a Stallbreaker approach by shutting down opponents' status/setup/recovery courtesy of Mold Breaker Taunt and bruteforcing through as much as your choice of coverage options lets you courtesy of your ability to straight-up ignore Unaware walls thanks to Mold Breaker. The niche Mega Gyarados fulfills for most Hyper Offense teams is crucial due to its fantastic matchup against Stall, and Stall only getting better as time passes gives this thing more and more room to just do its thing. Keep this thing in B+. Seriously.
Toxapex from A+ to A: Another HARD Disagree
Yeah, no. With Psychics falling out of favor as of lately this thing finds less of a reason to run a Payapa Berry. This allows Pex's options to be somewhat diversified as it no longer has to run Toxic in tandem with the berry to try crippling a Mega Latios or Mega Latias. In addition, Toxic Spikes is an invaluable support option that pressures switchins extremely heavily. TSpikes+Zygarde is broken for a reason, and Pex is the most consistent setter of TSpikes.
Nuking S or Dropping Landorus-Therian to A+: Disagree
As salty as I am about Zygarde not making the cut for S yet again (I heavily disagree with the reasoning, but I digress), this rank should still exist. Lando-T isn't what it used to be, but it's still a dominant force that I'd argue still makes the cut for S, and Heatran is, well... Heatran. It's the best thing in the tier and I'd argue it's been the best thing in the tier for a few months now. If stuff like Zygarde is what constitutes an A+ rank, the shit in this rank really does go above and beyond the rest. This shouldn't go anywhere, and I'm of the mindset that there should always be an S-rank.
Garchomp from B- to A-: Biggest Fucking Agree of My Life.
Remember when everyone thought this thing was shit? Well, it's not. I'd put my hands in fire to say that Garchomp is without a shadow of a doubt the single best purely-offensive Stealth Rock user in the tier (although its fatter Rocks sets are still great). It does a better job at dissuading VoltTurn shenanigans than most Lando-T variants since it blocks Volt Switch and it chips away at any U-turn users, and the two things that gave it even a semblance of a niche over the likes of Zygarde - Stealth Rock and Swords Dance - are what make this thing so incredibly powerful. Combining these two moves with Garchomp's good typing and fantastic stat distribution - base 102 Speed is still really fucking good - gives it the ability to tear every single Defogger in the tier that isn't Skarmory (which isn't that good right now) to shreds.
These calcs should speak for themselves. Chomp compresses a huge amount of stuff - including but certainly not limited to a great deal of the Landorus-T sets this thing was supposed to be outclassed by such as Bulky Z-Fly and Sash and Zygarde's awesome Ground/Dragon typing - into a behemoth that adds an ability that singlehandedly deters U-turn users and has enough Speed to perform such a crucial role. Garchomp's incredible wallbreaking abilities also let it muscle past Tangrowth, which is on the rise as of lately. Garchomp should absolutely rise, and it shouldn't be anything less than A-. I know it tends to be a little frowned-upon to suggest that something should move up more than one subrank, let alone a full rank (a full jump from B- to A-), but Garchomp has consistently proven it's indeed that good. It's just been slept on way too hard until recently.
Gengar from B to B- or C+: Disagree
I'd rather see Blacephalon rise to B than see Gengar drop to B- or even C+. Gengar has an incredible movepool that lets it run all the coverage it wants/needs to run (Blacephalon is unfortunately screwed out of even HP Fighting) while still allowing it to run the support options Gengar has historically been notorious for. Gengar was, is, and likely always will be a massive headache for most Stall teams to deal with since it puts so much pressure on Unaware Clefable, and with Stall being so good right now this niche is more valued than previously. Blacephalon can irritate Stall in a bevy of other ways, of course, but it wishes it could just get a better offensive movepool so it could feasibly run stuff like Taunt; this combined with Gengar's awesome Speed tier gives it a place in B over B- or C+, in my opinion.
Tangrowth from A to A+: Strongly Agree
Checking Zygarde is always going to be good, but Tangrowth's great min/maxed stats that let it tank hits from both ends of the spectrum and deal respectable damage from both ends of the spectrum, solid defensive typing that doesn't get Tangrowth's shit packed in by Iron Tail Zygarde, incredible ability that gives it enormous potential as a pivot with staying power, and diverse movepoool to hit almost anything it wants to for respectable damage (Sludge Bomb and Rock Slide have both recently seen some use) let it do so, so much more than just check Zygarde. I consider Tapu Bulu to be the superior choice in several situations - especially since BuluTran is such a tried-and-true core - but Tangrowth's benefits outside of this core are notable enough that it should be ranked alongside Bulu. Hell, it even has a favorable matchup against both members of that core if it opts to run Sludge Bomb. Regenerator cores are still dope as hell in this tier, and Tangrowth is still an integral part of many of these.
Crawdaunt to B-: Agree
I was a big proponent of Crawdaunt not long ago, and this still hasn't changed. If the C-ranks don't receive a massive overhaul Crawdaunt is definitely more at-home in B- since it adores a metagame that is more prone to getting cracked open by its absurdly powerful STABs.
Magearna to A+: Strongly Agree
This always felt a little weird in A to me. Setup variants are extremely good right now and need to be prepared for significantly more now.
Tapu Fini from B- to B: Agree
Yeah, it's just a bit better now. Not much more needs to be said.
Hydreigon from B- to B: Unsure, Leaning Towards Disagree
I'm gonna be really honest right now: I don't really get what the hype about this is/was. It's still a pretty solid check to Heatran but with Ash-Greninja opting to run Ice Beam significantly more often this thing tends to get blown back even before the Greninja gets a kill and transforms. I don't think it's necessarily bad, of course, but I don't feel like it's quite at that level though if it rises I understand why it should.
Mega Latios to A-: On the Fence
There was a point where this thing was the best Mega in OU and then Zam came in like a wrecking ball and almost completely eclipsed it. On one hand, Mega Latios can still check a great deal of the tier and can potentially benefit from the decline in Psychic-types by biting Pex back with a vengeance, should Pex opt to not run Payapa anymore; on the other hand, though, this thing hates how good Steelium-Z Heatran is at the moment since it can't even reliably check Tran like it used to. Part of me feels like a few metagame trends are going against it, but another part of me feels like it's being neglected to the point where it can bounce right back to being a huge threat, so I think we may have to wait a bit before we pass judgment on this guy.
Mega Zam to A: Disagree
Yeah, this is still one of the best Megas in the tier and it's still a right pain in the ass for a lot of teams to deal with. While it needing to run Timid a little more hurts it a bit, I still think it being in A+ is really reasonable.
Mega Mawile to S: Strongly Disagree
I could actually see this getting there in a couple months if it keeps this pace up, but it's not there yet. Probably the 4th-best thing in the tier right now, behind the two things in S and the snake that shits on your Ground immunities, but definitely not S-material yet.
Magnezone from A to A-: Disagree
This thing should never drop from A, in my opinion. With so many powerful Steel-types making an impact in the tier right now Magnezone still finds itself as good as ever at the one thing Magnezone has always been extremely good at: trapping Steels. Though a lot of these aforementioned Steels can live a hit from Magnezone and likely kill it back (that's assuming they're full, of course; any chip damage can prove extremely lethal when you see Magnezone in the team preview), this niche is still really good and it still has impeccable synergy with many top threats in this meta.
Mega Heracross up to B+: Agree
The only two things on Stall teams that actually beat this thing are Unaware Clefable and Moltres, and both have some form of opportunity cost that may discourage their use in some situations; Pyukumuku brings a lot to the table that neither Clefable nor Quagsire can bring, and Moltres isn't without its shortcomings as a Defogger since it can be so prone to entry hazards compared to other Defoggers. Mega Heracross has a movepool that was designed to shit on Stall and if Stall rises in viability (and it's currently rising in viability) so should Mega Heracross.
I also think Mega Sableye should rise to A-, since it's as much a set-in-stone Stall staple as Chansey, but I'm not gonna elaborate because everyone who's in the OU Discord is probably gonna think I want it to rise because of that Mean Look+Calm Mind set I've been messing around with lately. Please don't use that set. That is not an A- set.
Mega Gyarados from B+ to B: VERY STRONGLY Disagree
Yeah, I just can't see this thing being two subranks below vanilla Gyarados and I can't see vanilla Gyarados not being A- at worst (or at best tbh). I'd argue that it sharing a ranking with Mega Swampert isn't entirely unreasonable considering what archetypes these particular Megas fit on as well as what precisely they function as: powerful sweepers that fit on offensively-oriented teams that can dismantle walls in their own unique ways. While Mega Swampert can brute-force its way past incredibly bulky stuff due to its crazy Rain-boosted Waterfalls and solid coverage otherwise, Mega Gyarados takes more of a Stallbreaker approach by shutting down opponents' status/setup/recovery courtesy of Mold Breaker Taunt and bruteforcing through as much as your choice of coverage options lets you courtesy of your ability to straight-up ignore Unaware walls thanks to Mold Breaker. The niche Mega Gyarados fulfills for most Hyper Offense teams is crucial due to its fantastic matchup against Stall, and Stall only getting better as time passes gives this thing more and more room to just do its thing. Keep this thing in B+. Seriously.
Toxapex from A+ to A: Another HARD Disagree
Yeah, no. With Psychics falling out of favor as of lately this thing finds less of a reason to run a Payapa Berry. This allows Pex's options to be somewhat diversified as it no longer has to run Toxic in tandem with the berry to try crippling a Mega Latios or Mega Latias. In addition, Toxic Spikes is an invaluable support option that pressures switchins extremely heavily. TSpikes+Zygarde is broken for a reason, and Pex is the most consistent setter of TSpikes.
Nuking S or Dropping Landorus-Therian to A+: Disagree
As salty as I am about Zygarde not making the cut for S yet again (I heavily disagree with the reasoning, but I digress), this rank should still exist. Lando-T isn't what it used to be, but it's still a dominant force that I'd argue still makes the cut for S, and Heatran is, well... Heatran. It's the best thing in the tier and I'd argue it's been the best thing in the tier for a few months now. If stuff like Zygarde is what constitutes an A+ rank, the shit in this rank really does go above and beyond the rest. This shouldn't go anywhere, and I'm of the mindset that there should always be an S-rank.
Garchomp from B- to A-: Biggest Fucking Agree of My Life.
Remember when everyone thought this thing was shit? Well, it's not. I'd put my hands in fire to say that Garchomp is without a shadow of a doubt the single best purely-offensive Stealth Rock user in the tier (although its fatter Rocks sets are still great). It does a better job at dissuading VoltTurn shenanigans than most Lando-T variants since it blocks Volt Switch and it chips away at any U-turn users, and the two things that gave it even a semblance of a niche over the likes of Zygarde - Stealth Rock and Swords Dance - are what make this thing so incredibly powerful. Combining these two moves with Garchomp's good typing and fantastic stat distribution - base 102 Speed is still really fucking good - gives it the ability to tear every single Defogger in the tier that isn't Skarmory (which isn't that good right now) to shreds.
+2 252 Atk Garchomp Earthquake vs. 248 HP / 8 Def Tapu Fini: 288-340 (83.9 - 99.1%) -- 75% chance to OHKO after Stealth Rock and Leftovers recovery
252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 8 Def Tornadus-Therian: 370-436 (102.4 - 120.7%) -- guaranteed OHKO after Stealth Rock
+2 252 Atk Garchomp Outrage vs. 248 HP / 8 Def Tornadus-Therian: 466-550 (129 - 152.3%) -- guaranteed OHKO
+1 252 Atk Garchomp Devastating Drake (190 BP) vs. 80 HP / 84 Def Landorus-Therian: 463-546 (136.5 - 161%) -- guaranteed OHKO after Stealth Rock (even the fattest ones - which usually don't run Defog - get OHKOed after Stealth Rock)
252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 12 Def Moltres: 334-394 (87.2 - 102.8%) -- 18.8% chance to OHKO after Leftovers recovery (Variants that drop some HP in favor of more Defense still have a chance to get OHKOed unless they fully compromise their mixed bulk)
+2 252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 240+ Def Zapdos: 501-591 (130.8 - 154.3%) -- guaranteed OHKO after Leftovers recovery
+2 252 Atk Garchomp Earthquake vs. 248 HP / 252+ Def Scizor-Mega: 186-219 (54.2 - 63.8%) -- guaranteed 2HKO after Stealth Rock (The only shaky calc here: the Chomp user has to play around Curse a little should it be CurseZor and not a Defog variant but it only takes one wrong prediction on the Scizor user's end for this thing to ream it completely)
+2 252 Atk Garchomp Devastating Drake (190 BP) vs. 252 HP / 252+ Def Avalugg: 286-337 (72.5 - 85.5%) -- 81.3% chance to OHKO after Stealth Rock and Leftovers recovery (I know you're probably out of your mind if you think you're gonna see a situation like this happen ever but this proves that Chomp can muscle past even the most physically-bulky hazard remover in the entire tier if push comes to shove.)
252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 8 Def Tornadus-Therian: 370-436 (102.4 - 120.7%) -- guaranteed OHKO after Stealth Rock
+2 252 Atk Garchomp Outrage vs. 248 HP / 8 Def Tornadus-Therian: 466-550 (129 - 152.3%) -- guaranteed OHKO
+1 252 Atk Garchomp Devastating Drake (190 BP) vs. 80 HP / 84 Def Landorus-Therian: 463-546 (136.5 - 161%) -- guaranteed OHKO after Stealth Rock (even the fattest ones - which usually don't run Defog - get OHKOed after Stealth Rock)
252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 12 Def Moltres: 334-394 (87.2 - 102.8%) -- 18.8% chance to OHKO after Leftovers recovery (Variants that drop some HP in favor of more Defense still have a chance to get OHKOed unless they fully compromise their mixed bulk)
+2 252 Atk Garchomp Devastating Drake (190 BP) vs. 248 HP / 240+ Def Zapdos: 501-591 (130.8 - 154.3%) -- guaranteed OHKO after Leftovers recovery
+2 252 Atk Garchomp Earthquake vs. 248 HP / 252+ Def Scizor-Mega: 186-219 (54.2 - 63.8%) -- guaranteed 2HKO after Stealth Rock (The only shaky calc here: the Chomp user has to play around Curse a little should it be CurseZor and not a Defog variant but it only takes one wrong prediction on the Scizor user's end for this thing to ream it completely)
+2 252 Atk Garchomp Devastating Drake (190 BP) vs. 252 HP / 252+ Def Avalugg: 286-337 (72.5 - 85.5%) -- 81.3% chance to OHKO after Stealth Rock and Leftovers recovery (I know you're probably out of your mind if you think you're gonna see a situation like this happen ever but this proves that Chomp can muscle past even the most physically-bulky hazard remover in the entire tier if push comes to shove.)
These calcs should speak for themselves. Chomp compresses a huge amount of stuff - including but certainly not limited to a great deal of the Landorus-T sets this thing was supposed to be outclassed by such as Bulky Z-Fly and Sash and Zygarde's awesome Ground/Dragon typing - into a behemoth that adds an ability that singlehandedly deters U-turn users and has enough Speed to perform such a crucial role. Garchomp's incredible wallbreaking abilities also let it muscle past Tangrowth, which is on the rise as of lately. Garchomp should absolutely rise, and it shouldn't be anything less than A-. I know it tends to be a little frowned-upon to suggest that something should move up more than one subrank, let alone a full rank (a full jump from B- to A-), but Garchomp has consistently proven it's indeed that good. It's just been slept on way too hard until recently.
Gengar from B to B- or C+: Disagree
I'd rather see Blacephalon rise to B than see Gengar drop to B- or even C+. Gengar has an incredible movepool that lets it run all the coverage it wants/needs to run (Blacephalon is unfortunately screwed out of even HP Fighting) while still allowing it to run the support options Gengar has historically been notorious for. Gengar was, is, and likely always will be a massive headache for most Stall teams to deal with since it puts so much pressure on Unaware Clefable, and with Stall being so good right now this niche is more valued than previously. Blacephalon can irritate Stall in a bevy of other ways, of course, but it wishes it could just get a better offensive movepool so it could feasibly run stuff like Taunt; this combined with Gengar's awesome Speed tier gives it a place in B over B- or C+, in my opinion.
Tangrowth from A to A+: Strongly Agree
Checking Zygarde is always going to be good, but Tangrowth's great min/maxed stats that let it tank hits from both ends of the spectrum and deal respectable damage from both ends of the spectrum, solid defensive typing that doesn't get Tangrowth's shit packed in by Iron Tail Zygarde, incredible ability that gives it enormous potential as a pivot with staying power, and diverse movepoool to hit almost anything it wants to for respectable damage (Sludge Bomb and Rock Slide have both recently seen some use) let it do so, so much more than just check Zygarde. I consider Tapu Bulu to be the superior choice in several situations - especially since BuluTran is such a tried-and-true core - but Tangrowth's benefits outside of this core are notable enough that it should be ranked alongside Bulu. Hell, it even has a favorable matchup against both members of that core if it opts to run Sludge Bomb. Regenerator cores are still dope as hell in this tier, and Tangrowth is still an integral part of many of these.
Crawdaunt to B-: Agree
I was a big proponent of Crawdaunt not long ago, and this still hasn't changed. If the C-ranks don't receive a massive overhaul Crawdaunt is definitely more at-home in B- since it adores a metagame that is more prone to getting cracked open by its absurdly powerful STABs.
Magearna to A+: Strongly Agree
This always felt a little weird in A to me. Setup variants are extremely good right now and need to be prepared for significantly more now.
Tapu Fini from B- to B: Agree
Yeah, it's just a bit better now. Not much more needs to be said.
Hydreigon from B- to B: Unsure, Leaning Towards Disagree
I'm gonna be really honest right now: I don't really get what the hype about this is/was. It's still a pretty solid check to Heatran but with Ash-Greninja opting to run Ice Beam significantly more often this thing tends to get blown back even before the Greninja gets a kill and transforms. I don't think it's necessarily bad, of course, but I don't feel like it's quite at that level though if it rises I understand why it should.
Mega Latios to A-: On the Fence
There was a point where this thing was the best Mega in OU and then Zam came in like a wrecking ball and almost completely eclipsed it. On one hand, Mega Latios can still check a great deal of the tier and can potentially benefit from the decline in Psychic-types by biting Pex back with a vengeance, should Pex opt to not run Payapa anymore; on the other hand, though, this thing hates how good Steelium-Z Heatran is at the moment since it can't even reliably check Tran like it used to. Part of me feels like a few metagame trends are going against it, but another part of me feels like it's being neglected to the point where it can bounce right back to being a huge threat, so I think we may have to wait a bit before we pass judgment on this guy.
Mega Zam to A: Disagree
Yeah, this is still one of the best Megas in the tier and it's still a right pain in the ass for a lot of teams to deal with. While it needing to run Timid a little more hurts it a bit, I still think it being in A+ is really reasonable.
Mega Mawile to S: Strongly Disagree
I could actually see this getting there in a couple months if it keeps this pace up, but it's not there yet. Probably the 4th-best thing in the tier right now, behind the two things in S and the snake that shits on your Ground immunities, but definitely not S-material yet.
Magnezone from A to A-: Disagree
This thing should never drop from A, in my opinion. With so many powerful Steel-types making an impact in the tier right now Magnezone still finds itself as good as ever at the one thing Magnezone has always been extremely good at: trapping Steels. Though a lot of these aforementioned Steels can live a hit from Magnezone and likely kill it back (that's assuming they're full, of course; any chip damage can prove extremely lethal when you see Magnezone in the team preview), this niche is still really good and it still has impeccable synergy with many top threats in this meta.
Mega Heracross up to B+: Agree
The only two things on Stall teams that actually beat this thing are Unaware Clefable and Moltres, and both have some form of opportunity cost that may discourage their use in some situations; Pyukumuku brings a lot to the table that neither Clefable nor Quagsire can bring, and Moltres isn't without its shortcomings as a Defogger since it can be so prone to entry hazards compared to other Defoggers. Mega Heracross has a movepool that was designed to shit on Stall and if Stall rises in viability (and it's currently rising in viability) so should Mega Heracross.
I also think Mega Sableye should rise to A-, since it's as much a set-in-stone Stall staple as Chansey, but I'm not gonna elaborate because everyone who's in the OU Discord is probably gonna think I want it to rise because of that Mean Look+Calm Mind set I've been messing around with lately. Please don't use that set. That is not an A- set.