Pokemon that benefited most in the transition from BW to XY.

[Suicune Rider]

Name some of those, expecially ones you like.
For me, It's Clefable. I loved the pink fairy since like forever (I still remember the one I has on FR), but despite some of the best movepools in the game, it was always neglected; I just can't belive it's OU now!

 

[Zeb]

Bisharp: Defog buff, Knock Off buff, Steel no longer resisting Dark, Fairies giving Steel STAB more use.

Mandibuzz: Defog buff, Overcoat buff, Steel no longer resisting Dark.

Serperior: Contrary released, goes straight from PU -> BL within a few weeks.

Azumarill: Fairy typing gives it good offensive and defensive typing, BellyJet now legal thanks to egg moves removing limitations.

Scolipede: Speed Boost, nothing else to say really.

Crawdaunt: Knock Off buff and Steel nerf were pretty big for it, plus it got Aqua Jet as an egg move for tasty Adaptability boosted priority.


Megas: Kangaskhan, Charizard, Altaria, Mawile, Pidgeot, Pinsir, Beedrill, Manectric, Lopunny etc: were mons that were completely unviable, but became usable and in some cases big metagame threats

 

[Blue Cobra]

I think Scolipede has benefited the most with Speed Boost and an increased Attack stat.

I will also point out Stoutland and Exploud as Pokémon which have got a significant boost.

Stoutland has got an Attack boost from 100 to 110. Additionally, it can now learn Play Rough which is a very solid and powerful coverage move. It also helps it to deal with its only weakness: Fighting.

Exploud has got a fantastic weapon in the form of Boomburst. 140 base power without any side effects is awesome. Combine it with its Ability Scrappy and even Ghost types can avoid a mighty Boomburst from Exploud.

 

[Osprey]

The Snivy family used to be one of the most scorned of the starters thanks to their limited usefulness because of their shallow movepool. Now that Contrary is available to them, Serperior can hit like a train with Leaf Storm and Hidden Power alone.

Azumarill- it went from being a weak-ish Water type that I would ignore to a dragon-slayer that would frequently terrorize my online competitive team. It has a good defensive typing along with a ton of bulk, plus Huge Power to make an already painful Rough Play even scarier.

Beedrill. This was one of the bugs that set the low standards of Bug types, terrifying in concept alone. (I'm terrified of normal wasps. Meter-tall, extremely aggressive, sentient wasps? NOPE.) Then it got a Mega and now can outspeed the fastest Greninja and hit harder than the strongest Machamp. It even got Adaptability to boost its already high-powered attacks. Perfect glass cannon, in short.

Aggron, although not quite as much as the others above. It got two boosts: Assault Vest and Megavolution. AV's help cover Aggron's rather lacking Sp. Def, helping it to last longer... which is great for and Rock-Headed Head Smash user. Its Megavolution turns it into a defensive bastion, giving it incredibly high Defense and an Ability that reduces damage taken from supereffective attacks. Good luck with trying to take that thing down without Focus Blast.

Charizard. I know a lot of people hate this, but I'm a Charizard fan and I enjoyed the double fanservis. Megazard X gives it boosts to its Attack and lets it finally have STAB on the Dragon moves it can learn. Megazard Y goes for special attacking and is a good Pokemon for Harsh Sun strategies thanks to its Drought. Its Heat Wave is a force to be reckoned with. Also, normal Megazard X looks amazing, and shiny Y looks even better.

 

[Krash]

Kangaskhan got a huge boost from it's mega. Parental Bond makes it a sucker-punching bastard to deal with. Power-up punch also lends it some oomph.

Azumarill went from pointless to pretty cool, thanks to it's retype.

Scolipede. AH Scolipede...How I love your Speed Boost, Swords Dance, Baton Pass badassery.

 

[Winterdaze]

Dark types, period. The removal of the Steel resistance and the buff to Knock Off was just too good. Bisharp is pretty much the poster boy for the type's ascent, combining all those bonuses with newfound uses for its ability and Steel type moves.

Any Pokemon that became a Fairy also got a good boost, particularly Clefable who is now lauded as one of the most dependable defensive Pokemon in the game. Between good offensive coverage, great resistances and few weaknesses, there is almost no downside to becoming a Fairy type.

The ability to use any combination of egg moves where some were mutually exclusive before benefited many Pokemon too. Azumarill stands out among those, as Belly Drum and Aqua Jet were illegal together before.

And of course a lot of Pokemon that could use the previously useless Defog. Though a lot of the top Defoggers like Skarmory and the Latis were already good Pokemon, Mandibuzz is notable for rising dramatically from the depths due to its newfound utility and the buff to Overcoat.

 

[Rainami]

might as well avoid mentioning the ones mentioned in the thread, which I agree with aside from maybe stoutland, who I think suffered more of a nerf due to permasand no longer existing. Then again, permaweather not being a thing means that it's easier to keep sand up in the first place due to rain and sun being much more rare.

I wanna say my bby sableye got a significant buff, and I don't mean its mega because I don't think I need to bother explaining that, am just talking about vanilla sableye here. The buff was will-o-wisp's ascent to being an actually fairly reliable move. Okay, yeah, 85% accuracy isn't good, but previously it was only slightly better than Focus Blast. Focus Blast. I cannot overstate how much of a difference this actually makes. Sure, it sucks that fairies exist, but I think it's more important that I can actually use one its most important moves without drowning in my own sweat. Oh, knock off's buff is cool too. But mostly will-o-wisp.

another one is galvantula. While the (completely unfair) thunder nerf is lame for it, sticky web gives it much more use than it had before. Should probs mention shuckle in this same post actually. While neither of these pokemon are great, they're the best sticky web setters there are (along with maybe smeargle I guess...), which gives them a very notable niche, somefin they couldn't really claim before xy.

last and definitely least, flareon. I feel like mentioning it because after five generations, it finally got what it wanted for so long -- a move. It's still flareon, it still kinda sucks, but it sucks while hitting like a nuclear warhead, and in the end, isn't that what's really important?....wait, it's not?

 

[winstein]

One way to see what Pokemon improve is to see the moves that improved as a result. Two of the big ones are Defog and Knock Off. I think those two new introductions are what caused newer Pokemon to rarely learn those moves. For Knock Off, it used to be that many Pokemon can learn it, but now? Only a handful of new Generation 6 Pokemon learns this powerful move. Defog is a bit different since it wasn't useful in Generation 5, but no new members get this move.

You can name the more useful Pokemon as the ones that benefit from Defog, but I feel that the lesser-known Defog Pokemon deserves the mention in this case. Pelipper used to be outperformed by many things since Defence is its only strength, but with Defog, it could be considered over, say, Mantine, another Defog Pokemon who is useful. Shiftry is another unusual learner, but since its type is different from the typical user, it could be useful. Defog's usefulness even makes Lumineon, of all things, cool. It also made those abilities that punish stat-lowering effects much better, namely Defiant, Competitive and Contrary. It would actually be interesting if Defog is an HM in HeartGold and SoulSilver, just to see if Defog's effect change with the few natural learners can be as impactful.

Knock Off is not as revolutionary as Defog, but it certainly adds a powerful Dark-type attack to many learner's movepool, and due to its reasonable power and almost-guaranteed max power, you can see how it revolutionise Physical attacking. Since Dark is a good offensive type that gets past Steel-types, it made them much better.

The changes could have pointed out how Ghost-type gets a lot of benefits, with Steel not resisting it and now being immune to trapping, but it doesn't seem to be as impactful as above. The most it would happen is that Ghost-types have an easier time on the offence and defence, but not game-changing in the way Dark is, likely because Ghost is weak to the now-popular Dark (and they have an arsenal of tricky attacks that hurt them, like Pursuit, Sucker Punch and now Knock Off). Not even Hex's power increase made things easier since status is not as easily dealt unless you specifically want to inflict them. Of course, it doesn't help that most Ghost-types have stat distributions that either don't comply with their movepool or they are not high enough to be impactful.

Thanks for reading.