May I present you this?
Mewtwo-Mega-Y @ Choice Specs
Ability: Tinted Lens
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
IVs: 0 Atk
- Psycho Boost
- Moongeist Beam/Overheat
- Trick/Secret Sword/Moonblast
- Volt Switch/Ice Beam
This set, under psychic terrain support, kills most opponents with Psycho Boost, sometimes even the sturdiest ones. At full health.
Calcs made considering Psychic Terrain.
252+ SpA Choice Specs Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Zygarde-Complete: 570-672 (89.6 - 105.6%) -- 37.5% chance to OHKO
252+ SpA Choice Specs Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Audino-Mega: 469-553 (114.3 - 134.8%) -- guaranteed OHKO
252+ SpA Choice Specs Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Giratina: 486-573 (96.4 - 113.6%) -- 81.3% chance to OHKO
252+ SpA Choice Specs Tinted Lens Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Registeel: 414-486 (113.7 - 133.5%) -- guaranteed OHKO
If Registeel can't take the hit, then aegislash can't neither.
252+ SpA Choice Specs Tinted Lens Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Celesteela: 546-642 (137.1 - 161.3%) -- guaranteed OHKO
252+ SpA Choice Specs Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 252+ SpD Kyogre-Primal: 394-465 (97.5 - 115%) -- 81.3% chance to OHKO
Not even imposter chansey can switch very well on psycho boost.
252+ SpA Choice Specs Tinted Lens Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 0 SpD Eviolite Mewtwo-Mega-Y: 436-514 (61.5 - 72.5%) -- guaranteed 2HKO
Without eviolite it risks the OHKO.
252+ SpA Choice Specs Tinted Lens Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 0 SpD Mewtwo-Mega-Y: 654-770 (92.3 - 108.7%) -- 56.3% chance to OHKO
Deinvesting your own spdef grants you something like 10% more damage, which ensures the KO without eviolite.
Our winner is Solgaleo, which double resists (and thus resists) Psychics moves; it avoids the OHKO with every move; Moongeist Beam becomes the best move.
252+ SpA Choice Specs Mewtwo-Mega-Y Moongeist Beam vs. 252 HP / 252+ SpD Solgaleo: 378-446 (79 - 93.3%) -- guaranteed 2HKO
130 bp and super effectiveness is required to OHKO it, and is provided by Overheat.
252+ SpA Choice Specs Mewtwo-Mega-Y Overheat vs. 252 HP / 252+ SpD Solgaleo: 492-580 (102.9 - 121.3%) -- guaranteed OHKO
Pratically 1 layer of spikes ensures the KO on anything not named chansey, blissey or solgaleo.
Dark type are obviously immune, but we have room for coverage.
252+ SpA Choice Specs Mewtwo-Mega-Y Moonblast vs. 252 HP / 252+ SpD Gyarados-Mega: 278-328 (70.5 - 83.2%) -- guaranteed 2HKO
I've never seen Gyarados invested in spdef, but moonblast 2OHKOs anyway.
252+ SpA Choice Specs Mewtwo-Mega-Y Moonblast vs. 252 HP / 252+ SpD Yveltal: 338-398 (74.1 - 87.2%) -- guaranteed 2HKO
Ice beam is close enough btw.
Obviously mtar can't survive secret sword at all.
Greeninja can't switch on coverage moves, but outspeeds this mmy set.
Ice beam is there only for zygarde, as it OHKOs it no matter what.
Moongeist beam is nice coverage and helps with shedinja.
It easy to manage for the porpoise of imposter proofness, by selecting walls appropriate for the coverage moves and by considering that the imposter will have his spatk probably halved and will miss the extra, coveted power given by the specs.
I think it's possible to run adaptability to destroy stuff, but negating x2 resist is invaluable to me.
I'll now post results from the adaptability set.
Mewtwo-Mega-Y @ Choice Specs
Ability: Adaptability
EVs: 252 SpA / 4 SpD / 252 Spe
Modest Nature
IVs: 0 Atk
- Overheat/Magma Storm
- Psycho Boost
- Fleur Cannon
- Moongeist beam/Secret Sword
The moveset is changed, you may notice how it is all about cutting your own spatk so that chansey can't countersweep.
I'm not posting changes on the result of Psycho Boost if Tinted Lens wasn't necessary, the rule of thumb is: if it was close to the OHKO, now it scores one. Maudino, Tina, Garde-C are vaporized on the spot. Unless they carry an assault vest I guess.
Pokemon not shown are assumed to run 252 HP / 252+ SpD.
This set requires a LOT more prediction; you should click Psycho Boost UNLESS you expect something that resist it AND is weak to your coverage OR is Shedinja.
There is a lot of stuff that can go wrong and you don't want that. Moongeist beam is worth only of shedinja. You can be double resisted only by psychic/steel and Overheat outdamages Moongeist Beam. If your opponent is a psychic type then Psycho Boost still is stronger (140*2(STAB)*1.5(Psychic Terrain)*0.5(Resist)>100*2(Super Effective)). If it's a steel type Overheat does the trick.
How Registeel lives the day? At 62.5% it doesn't.
252+ SpA Choice Specs Mewtwo-Mega-Y Overheat vs. 252 HP / 252+ SpD Registeel: 340-402 (93.4 - 110.4%) -- 62.5% chance to OHKO
Aegislash dies
252+ SpA Choice Specs Mewtwo-Mega-Y Overheat vs. 252 HP / 252+ SpD Aegislash-Shield: 340-402 (104.9 - 124%) -- guaranteed OHKO
Celesteela is not just bulky enough.
252+ SpA Choice Specs Mewtwo-Mega-Y Overheat vs. 252 HP / 252+ SpD Celesteela: 452-532 (113.5 - 133.6%) -- guaranteed OHKO
I forgot mgross before but he's not liking it too.
252+ SpA Choice Specs Mewtwo-Mega-Y Overheat vs. 252 HP / 252+ SpD Metagross-Mega: 428-504 (117.5 - 138.4%) -- guaranteed OHKO
M-tar gets close enough to the OHKO.
252+ SpA Choice Specs Mewtwo-Mega-Y Fleur Cannon vs. 252 HP / 252+ SpD Tyranitar-Mega: 402-474 (99.5 - 117.3%) -- 93.8% chance to OHKO
Obvioulsy SR ensures the OHKO on everything with a chance of survival listed here.
Now: what can reliably survive this?
Well because of our moveset the answer is "
imposter chansey".
252+ SpA Choice Specs Adaptability Mewtwo-Mega-Y Psycho Boost vs. 252 HP / 0 SpD Eviolite Chansey: 291-343 (41.3 - 48.7%) -- guaranteed 3HKO
But in reality it also depends on you selecting the correct move. Selecting the wrong move might just tickle the opponent, and running an ability that patches a weakness isn't that rare. Scout the opponent before risking.
Other options:
Moongeist Beam kills shedinja, Overheat kills most stuff that resists Psycho Boost, but Magma Storm does both at the cost of being inaccurate and the fact that most OHKOs Overheat reaches are there by just a little, meaning that they will act on their turn (while dying at the end of it).
Secret Sword really helps with m-tar under the sand while wearing an assault vest. Added point it doesn't risk the miss and bypasses surprise flash fire stuff.
Volt switch may be used to maintain momentum, trick can be used to cripple walls but then mmy lose his reason to live.
What if chansey switches and survives?
First, does it have its spatk halved? If yes it's not a problem, your average, non dedicated wall can handle it. Registeel for example may lose 40% of his HP to Overheat, but it's just that.
If it doesn't then you have a problem. You'll need to predict the correct move or run a dedicated wall for this occasion, or else one of your mon will die. More if you play it bad.
How to use this set:
Safe switch it on something that can't outspeed mmy. Scout for scarf. Psychic Terrain stops priority and is nice both for defense and offence. Fire your nuke, hope for the best. Switch out if you get a bad matchup or if you have -2 spatk. Repeat when needed.