I have a lot of sets to post :D
Xerneas @ Choice Specs
Ability: Fairy Aura
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
- Moonblast
- Thunder
- Aromatherapy
- Grass Knot
There's probably a better set out there for specs xern but I just clicked moonblast most of the time anyway. Has a lot of immediate power and wall-breaking capabilities without having to set up, and honestly serves as a crucial way of breaking fat teams that I faced a good amount of the time. I believe I had a better darkrai check on this team so I wasn't using sleep talk, but when I did use sleep talk I used it with just 2 attacks (rocks are so easy to get in ubers with pdon and moonblast 2hkos ho-oh). Moonblast has 2hkod some offensive variants of pdon with rocks which I thought was p neat. Thunder just for ho-oh and gknot hits arceus-water/ground and pdon/ogre harder. Probably a better variant of the set can be found
here
Kangaskhan-Mega @ Kangaskhanite
Ability: Scrappy
EVs: 248 HP / 36 Atk / 224 Def
Impish Nature
- Fake Out
- Body Slam
- Low Kick
- Seismic Toss
Pretty neat check to ekiller. Fake out and 36 attack are used so that fake out + low kick can KO 100% arceus. Rest is put in defense so that it can take +2 LO espeeds p handily. Body slam has a 51% para rate and limits any sort of offensive switch-ins. Seismic toss does 200 damage so after para-ing something like Lugia you can beat it, and it can even 2hko pdon with rocks. it really eats alive defensive pokemon like ferrothorn or klefki, both of which are 2hkod. Low kick is only used so that it can KO arceus while still investing as much in defense as possible. I considered counter on this but it's mostly useless. Still, counter will do 4x damage due to parental bond, and OHKO after being hit by almost any physical attack. I just figured body slam neuters most offensive mons anyway.
+2 252 Atk Life Orb Arceus Extreme Speed vs. 248 HP / 224 Def Mega Kangaskhan: 261-308 (63.1 - 74.5%) -- guaranteed 2HKO
(always lives after 2 rock switch-ins)
(couldn't find a gif lol)
Arceus-Fairy @ Pixie Plate
Ability: Multitype
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Judgment
- Stone Edge
- Calm Mind
- Earth Power
Cool ho-oh lure. If someone sees an arceus-fairy, the first thing they're doing is switching to pdon or ho-oh. The "prediction" to pick the coverage move is really basic because arceus-fairy hardly runs sets like this. I thought about running a -spdef nature but it's pointless because I didn't want to invest in so much attack to OHKO ho-oh anyway. Because judgment + stone edge always KOs ho-oh regardless of nature (assuming 0 attack), changing the nature would be unnecessary. Fire blast or recover are optional over CM, but I like the ability to boost vs bulkier teams (especially considering how few appreciate fairy STAB that can touch pdon and ho-oh). Fire blast would simply hit ferrothorn if you don't want to be hard-walled by anything.
Kyogre-Primal @ Blue Orb
Ability: Primordial Sea
EVs: 192 HP / 252 SpA / 64 Spe
Modest Nature
- Origin Pulse
- Thunder
- Ice Beam
- Sleep Talk
Mostly standard set with sleep talk opposed to calm mind or whatever else it would normally use. Just a cooler way to check darkrai (always pulls a good roll on sleep talk). Unfortunately I missaved max attack adamant when I used this lol
Slowbro-Mega @ Slowbronite
Ability: Regenerator
EVs: 248 HP / 252 Def / 8 Spe
Bold Nature
- Ice Beam
- Iron Defense
- Yawn
- Slack Off
One of the only mons to counter m-mence, ho-oh, and ekiller. It's far bulkier than lugia and, when mega'd, is a better counter to those 3 mons. Set is p basic, I used toxic>yawn one week and accidentally used calm mind the first week. Toxic can cripple things like lugia but I like yawn with hazards up because it essentially forces 1 thing to go to sleep (endlessly switching with rocks up obviously won't work).
Groudon-Primal @ Red Orb
Ability: Desolate Land
EVs: 104 HP / 252 SpA / 88 SpD / 64 Spe
Modest Nature
- Rock Polish
- Fire Blast
- Dragon Pulse
- Solar Beam
Fair warning: you should probably use precipice blades with a -def (or spdef) nature opposed to dragon pulse. I just really liked the ability to nail m-mence because that thing's a cunt to most of my teams. To be fair, there are very few targets pblades even hits outside of kyogre and blissey. I figured if I actually played one of those (which I did), no one would switch them in on me anyway. Idea is that fire blast is far stronger on things like lugia than any physical attack groudon can use. Solar Beam eats alive water-ceus, probably the best check to pdon. You wouldn't believe how satisfying it is to hit a solar beam on arceus-water -
Arceus-Fighting @ Fist Plate
Ability: Multitype
EVs: 4 Atk / 252 SpA / 252 Spe
Naive Nature
- Judgment
- Ice Beam
- Stone Edge
- Calm Mind
Same exact idea as the fairy arceus. Only reason I used this instead is because it's a pretty great offensive check to ekiller.
252 SpA Fist Plate Arceus-Fighting Judgment vs. 4 HP / 0 SpD Arceus: 318-374 (83.2 - 97.9%) -- guaranteed 2HKO
Otherwise Fairy arceus is probably a better lure unless you notice your team might have some issues with ekiller.
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Blaziken @ Focus Sash
Ability: Speed Boost
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Protect
- Baton Pass
- Low Kick
Diancie-Mega @ Diancite
Ability: Magic Bounce
EVs: 216 HP / 252 Atk / 36 Spe
Naughty Nature
- Diamond Storm
- Moonblast
- Magnet Rise
- Protect
Giratina-Origin @ Griseous Orb
Ability: Levitate
EVs: 248 HP / 248 Atk / 12 Spe
Adamant Nature
- Shadow Force
- Shadow Sneak
- Earthquake
- Defog
Probably my favorite core that I used UPL, and the only one that didn't work :(. Blaziken pass is really nasty to any team. I originally had kanga>diancie but the appeal of being able to bypass whirlwind from lugia and toxic was too tempting. I totally forget what the 36 speed was for, but I think it was for mega gar when diancie is at +1? Not sure.
You just click diamond storm a lot unless they have a high-health pdon or a ground-ceus. Diamond Storm at +2 eats klefki alive so there's no reason to run any sort of coverage or anything. Magnet rise will allow diancie to just 2hko pdon with diamond storm. Diamond storm at +2 OHKOs Offensive Arceus, Fat Xerneas, Kangaskhan, Primal Ogre, and just about anything else not phdef. Diancie is also surprisingly bulky w/ this much HP, especially without having mega-evolved.
Calcs:
+2 252+ Atk Mega Diancie Diamond Storm vs. 248 HP / 248+ Def Primal Kyogre: 324-382 (80.3 - 94.7%) -- guaranteed 2HKO
+2 252+ Atk Mega Diancie Diamond Storm vs. 252 HP / 200+ Def Arceus-Water: 276-325 (62.1 - 73.1%) -- guaranteed 2HKO
+2 252+ Atk Mega Diancie Diamond Storm vs. 252 HP / 56+ Def Primal Groudon: 243-286 (60.1 - 70.7%) -- guaranteed 2HKO
+2 252+ Atk Mega Diancie Diamond Storm vs. 248 HP / 0 Def Klefki: 226-267 (71.2 - 84.2%) -- guaranteed 2HKO after Leftovers recovery
I picked giratina as another recipient that could directly be passed to on Groudon. Shadow force is really strong.. 248 HP was used because I had enough insurance vs the physical attackers it's meant to check and because I want a BP recipient to be as bulky on both sides as possible. Giratina passes as both a BP recipient and a defogger -
Mewtwo @ Choice Specs
Ability: Pressure
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Psystrike
- Ice Beam
- Shadow Ball
- Fire Blast
I hate how LO mewtwo gets worn down especially considering it just clicks psystrike most of the time anyway. Shadow ball because I didn't really see a point in focus blast and OHKOing other mewtwo is nice considering how much of a nuisance it can be to face. In my game it only hindered me to be specs (except not getting worn down to giratina-o revenge range) so the set didn't really work but I still think it was the better choice for my team.
Edit: Forgot about BW sets.
Latias @ Soul Dew
Ability: Levitate
EVs: 252 HP / 120 SpD / 136 Spe
Calm Nature
- Calm Mind
- Roost
- Roar
- Dragon Breath
Twist on spdef Latias. CM>light screen (idk if this is an actual thing but that's what the smogon analysis sugested) and dragon breath allows it to para fast threats and 1v1 things like cm arceus.
Arceus-Water @ Splash Plate
Ability: Multitype
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Swords Dance
- Waterfall
- Dragon Claw
- Extreme Speed
Idk if this is super-rare in BW but it's a really neat set. Also I used it in ORAS and it can work p well, although eq should be ran over espeed to nail Pdon. Eq can be ran in BW too to beat Dialga.
Groudon @ Rocky Helmet
Ability: Drought
EVs: 248 HP / 8 Atk / 252 Def
Relaxed Nature
- Stealth Rock
- Earthquake
- Stone Edge
- Fire Blast
Helmet Don is cool because it can weaken physical attackers and punish genesect u-turns. I specifically used this so that terrak CC would 100% OHKO arceus with prior damage from helmet.
Darkrai @ Choice Scarf
Ability: Bad Dreams
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Trick
- Dark Void
- Dark Pulse
- Haze
lol this set is admittedly kind of stupid in XY (where it was used). I wanted an offensive check to xern and I figured darkrai could haze and outspeed it at +2. Dark Void is kind of a thing some teams just have to "accept", so making it a little faster doesn't really hurt at all. You can trick away the scarf to some fat check like klekfi, or wait until late-game when dark pulse can do some damage to offensve maybe.