Is there any special attack that can OHKO Blissey?

Question

Aside from Psyshock, Blissey being 252 Hp, 252 SpD.

Comments

Aside from Psyshock? Psystrike :P

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But I believe that even Pyshock and Psystrike don't OHKO Blissey.

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Actually Modest Mega Mewtwo Psystrike does OHKO Blissey so yeah but aside from Psyshock or Psystrike.

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The answer is obviously yes. Any Pokemon can be OHKO'd (with the obvious exceptions like Sturdy, but even then there are multi-hit moves). One quick calc can prove this:
+6 252+ SpA Mega Mewtwo Y Psychic vs. 252 HP / 252+ SpD Blissey on a critical hit: 765-901 (107.1 - 126.1%) -- guaranteed OHKO
(765, 774, 783, 792, 801, 810, 819, 828, 837, 846, 855, 864, 873, 882, 891, 901)

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Do stat changes count?

Answer 1

>But I believe that even Pyshock and Psystrike don't OHKO Blissey.
commented 3 minutes ago by Crimson1

You're wrong.

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>252+ SpA Keldeo Secret Sword vs. 252 HP / 4 Def Blissey: 1256-1478 (175.9 - 207%) -- guaranteed OHKO

Keldeo OHKOs. However do note, Blissey with 252 Defense And a postive Defense Nature will survive it.
>252 SpA Mewtwo Psystrike vs. 252 HP / 4 Def Blissey: 765-901 (107.1 - 126.1%) -- guaranteed OHKO

Same case as Keldeo's Secret Sword

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The closest you will get WITHOUT ANY DROPS OR INCREASES IN SPECIAL ATTACK OR DEFENSE is probably this;
>252+ SpA Choice Specs Kyogre Water Spout (150 BP) vs. 252 HP / 252+ SpD Blissey in Rain on a critical hit: 589-694 (82.4 - 97.1%) -- 62.5% chance to OHKO after Stealth Rock

Yes Specs Kyogre in Rain is stronger than Specs Kyurem-W

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I know you said that Psyshock isn't counted but Psyshock is lower base power than Psystrike, and can OHKO too;
>252+ SpA Mega Alakazam Psyshock vs. 252 HP / 4 Def Blissey: 742-874 (103.9 - 122.4%) -- guaranteed OHKO
252 SpA Choice Specs Alakazam Psyshock vs. 252 HP / 4 Def Blissey: 832-979 (116.5 - 137.1%) -- guaranteed OHKO

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Anyway to sum up - No, nothing can OHKO Blissey as an unboosted Special Attack barr Secret Sword, Psystrike, Psyshock and Water Spout by Specs Kyogre on a crit in rain with Stealth Rock support.

However do remember, once you factor in boosts and drops, many special attacks can kill Blissey. For example;
>+6 252 SpA Gengar Sludge Bomb vs. -6 252 HP / 252+ SpD Blissey: 1371-1614 (192 - 226%) -- guaranteed OHKO

Comments

What about sheer cold?

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I think he means aside from moves that are specifically designed to ohko, noby.

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Most blissey are heavily defense invested,  so Secret Sword usually won't 0hko.

Answer 2

Psystrike and Sacred Sword are other alternatives to slay blissey with a Special move but other than those and Psyshock, almost no special attack slays Blissey without any status drops.

Why, a fully invested Kyurem-W can't take out a Blissey with Specs-Boosted Draco Meteor on Critical hit. With Special Defense drops though, it is possible to defeat Blissey with a Special Attack.

Comments

Yeah I know I was wrong I calculated it afterwards.

Answer 3

252+ SpA Choice Specs Solar Power Charizard Blast Burn vs. 252 HP / 4 SpD Blissey in Sun: 616-726 (86.2 - 101.6%) -- 12.5% chance to OHKO

Comments

Blissey is supposed to have 252 SpD EVs according to the question.