Some of the biggest changes in VaporeMons come from voted-in Pokemon Adjustments and signature items, as these submissions were able to directly change a Pokemon into becoming potentially OU-viable, which worked in many cases.
Meloetta-Pirouette
Using the Dancing Shoes item, Meloetta can transform into its Pirouette form on switch-in, while also gaining a hazard immunity and immunity to sound moves. Additionally, both Meloetta forms received some big specific changes, with Melo-P now having the ability No Guard (accessed by setting base Meloetta's ability to Trace and having it hold Dancing Shoes) and great new moves in Mega Kick and Rapid Spin. Melo-P is basically NatDex Mega Lopunny, being a fast, strong, and not super frail pivot, able to bully teams over the course of an entire game. Note when building that Melo-P no longer learns Sing (due to No Guard) and Swords Dance (due to it being broken with its power and Speed).
Crabominable
Crabominable is now a Fighting/Water-type with Fur Coat and a ton of new viable moves like Slack Off, Jet Punch, Swords Dance, and Storm Throw (Fighting-type Flower Trick). With these tools, Crabominable is a premier physical wall that goes well into the likes of Great Tusk and Kingambit, as well as being one of the best wincons in the metagame thanks to Swords Dance + Jet Punch + Crab's 132 Attack.
Iron Jugulis
Aside from the previously mentioned Neuron Drive over Quark Drive, Iron Jugulis received one very simple change that's made it one of the most terrifying breakers in the meta: Mega Launcher. 120 BP Dark Pulses from a mon with 122/108 special offense is pretty hard to handle defensively, especially with Jugulis has its very powerful STAB Hurricanes to hit most Dark resists, with your choice of Flamethrower or Earth Power covering most others.
Jolteon
Mentioned earlier when I went over Battle Spines, Jolteon has gone from a lower tier hero to THE fast Electric-type of the metagame and it's all thanks to the aformentioned Battle Spines, plus two crucial coverage moves in Dazzling Gleam and Overheat. Jolteon's poor bulk still makes it somewhat difficult to get in, but once in, Jolteon is almost guaranteed to leave a dent in something, as you'll either have to take a strong Thunderbolt + 12.5% chip, have your Grass-type torched by Overheat + 12.5% chip, or have your Great Tusk or Ting-Lu chunked by a Dazzling Gleam + 12.5%, while it always has the option to simply Volt Switch out, complete with that added 12.5% Battle Spines chip. If you've found yourself missing the likes of Tapu Koko or Zeraora, look no further than Jolteon to fill your fast Electric needs.
Magnezone
Magnezone is one of the top pivots in the tier thanks to it gaining Levitate and Rapid Spin, plus recovery in the previously mentioned Rebuild. This makes Magnezone an extremely consistent spinner, easily coming in on Ground-type moves from common hazard setters like Landorus-T and Ting-Lu, while being able to deal decent damage to Gholdengo with Volt Switch or Software Crash unlike the eternally walled Corviknight. Magnezone's pretty deep movepool also makes it more versatile than ever, between being an offensive pivot, defensive pivot, Assault Vest pivot, or classic Magnet Pull sets that can be either choiced to IronPress. If you need a good glue mon on your team, Magnezone could very well be your answer.
Milotic
Milotic was given the often wanted Water/Fairy-typing, along with two great abilities in Sheer Heart and Water Veil (which now gives you the Aqua Ring effect on switch-in). This makes Milotic one of the premier defensive pivots in the metagame, handling the likes of Dragapult, Iron Valiant, Great Tusk, and Samurott-H, while also having the option to become a dangerous wallbreaker or cleaner with Sheer Heart.
Landorus-Therian
Landorus-T has actually received a fair number of buffs over the course of VaporeMons and, while it still functions the same as always for the most part, Lando's inherent versatility means that it always loves having more options. Landorus gained great moves in Defog, Spikes, Acrobatics, and Natural Gift, while its commonly used Smack Down was buffed to 65 BP, making it much more usable. Lando also greatly benefitted from losing Gliscor as competition, making it once again one of the best Ground-type pivots, even with Great Tusk having pivoting now.
Delphox
Delphox is now a Fire/Fairy-type, a never before seen but extremely powerful typing, giving it a ton of unique offensive and defensive strengths. Fire Blast + Moonblast + Psychic/Focus Blast/Grass Knot hits nearly everything, with Fire Blast being super powerful thanks to the 1.2x boost from Blaze, it can boost up with Nasty Plot, pivot with Round, heal with Rekindle or Wish, act as hazard control with Court Change, cripple foes with Will-O-Wisp or Thunder Wave, and switch into Iron Valiant's dual STAB, and probably do even more things. Only fitting for magician to be this versatile.
Toxapex
Toxapex is still a pretty notable defensive presence in the tier, but ironically its major changes have more or less been a nerf to it overall. Toxapex is now Dark/Water and gained a ton of good new moves in Knock Off, Body Press, Super Fang, Snatch, and Wash Away. This new typing completely changes what kinds of Pokemon Toxapex can take on, now handling the likes of Gholdengo, Dragapult, and Kingambit while no longer being able to take on Iron Valiant or Ogerpon forms. While becoming a Dark-type did end up being a nerf overall, Toxapex's huge bulk, Regen, and much deeper movepool still make it a premier wall in the tier, plus it makes for fun Regen cores with Slowking-Galar since it doesn't stack a weakness with it anymore.
Honorable Mentions
Scyther line - Scyther was already mentioned when I talked about Steadfast earlier, but the other reaosn why it's a genuine threat is thanks to the Scyther line's new signature item, Mantis Claw. This item gives each mon in the Scyther line an immunity to hazards while also giving them a boost to their stats: 1.5x Speed for Scyther, 1.3x Def and SpD for Scizor, and 1.5x Attack for Kleavor.
Rotom - Regained Defog and Pain Split, while each Rotom form also gained 1 new STAB, with Rotom-Wash getting the amazing Wash Away.
Diancie - Got a new signature item in Diancite Stone Fragment, which changes its ability to Magic Bounce and raises its Atk, SpA, and Spe by 1 stage on switch-in, making Diancie into a mini-version of Mega Diancie. Also loves having pivoting in Rollout and priority in Accelerock.
The Loyal Three - Each of the Loyal Three gained some pretty substantial changes. Okidogi got Intimidate, Parting Shot, and Swords Dance, Fezandipiti got Neutralizing Gas, Will-O-Wisp, Defog, and Healing Stones, and Munkidori got Magic Guard and Psycho Boost. Each member also gained the Toxic Spikes-setting Dire Claw.
Muk & Muk-Alola - If you're sad about Toxapex no longer being Poison/Water, there's a half-decent replacement in Muk, who's now Poison/Water with Regenerator and a bunch of new moves like Wave Crash, Swords Dance, Earthquake, and Recover. Muk-Alola also received a bunch of buffs and is actually the much more viable of the two, gaining Neutralizing Gas, Swords Dance, Recover, Earthquake, Stealth Rock, and Sucker Punch.
Mew - Mew has two great abilities in Synchronize and Protean, along with some big movepool buffs in Defog and Recover.
Tinkaton - Gained new utility in Defog, Rebuild, and Counteract, as well as more offensive power in the ability Blunt Force (1.5x Attack but your moves can't hit super effectively), making Tinkaton a lot easier to use both offensively and defensively.
Wigglytuff - Gained the signature item Tuffy-Tuff, which doubles its defenses, along with new abilities in Wind Rider (which blocks Defog now) and Natural Cure, and new moves in Boomburst, Moonblast, Tidy Up, Spirit Break, and Teleport.
Bellibolt - Mini-Rotom-Wash and Zapdos in one, now being Electric/Water with Static and Volt Absorb, utility in Wash Away, and coverage in Ice Beam and Earth Power.
Decidueye(-Hisui) - Alolan Decidueye gained Contrary, letting it potentially break through teams with Leaf Storms and Shadow Balls, while Hisuian Decidueye is now Ghost/Fighting with Poltergeist, being a very powerful but slow wallbreaker.
Revavroom - Through the Star Shard items, Revavroom gains access to 5 new forms based on the Starmobiles from Scarlet and Violet's story. All of them can be somewhat threatening sweepers in their own right, but the best of them is actually used in a utility role as Revavroom-Ruchbah's Misty Surge activates Iron Valiant's Rune Drive and, unlike the mostly more viable Weezing-Galar, Revavroom can use Rollout or Parting Shot to get Valiant in safely.
Charizard - Similar to Revavroom, Charizard also has 2 signature Tera Shard-like items, both of which mirror the Mega stones of generations past. The Charizardite Shard X turns Charizard into a Dragon-type (before hazards damage), gives it Tough Claws, a 1.2x boost to Dragon and Fire moves, and a +1 Attack boost, with the Charizardite Shard Y turns Charizard into a pure Fire-type (also before hazard damage), gives it Drought, a 1.2x boost to Fire and Flying moves, and a +1 SpA boost. Despite the boosts being a bit much, Charizard is still a very rare sight, with Zard X being a bootleg Haxorus, and Zard Y being basically Chi-Yu, but somehow not that viable.
