Here's the best results I could find for each type, under the assumption that all sets must be legal in an Anything Goes match with just one Pokemon per side, and that for moves that care about the number of times they've been used (Rollout, Fury Cutter, Ice Ball, Trump Card, and any move boosted by Metronome) only the first hit counts.
Normal
Mewtwo @ Choice Specs
Ability: Pressure
EVs/Nature: max SpA
Me First
Calm Mind
Snatch
blank move
-vs.-
Smeargle @ Mewtwonite Y
Level: 1
Ability: Moody
IVs/EVs/Nature: irrelevant
Stockpile
Spit Up
Conversion
Magic Room
And you thought Explosion was the most powerful Normal move in the game. Moody is an amazing ability in best-case-scenario brainstorming, allowing selective buffs or debuffs to any and all stats without even using up a move slot. Similar to the great Embargo above, Mewtwo starts out with Me First on turn 1 which fails against Smeargle's Magic Room, then builds up Calm Minds while Smeargle does a fat lot of nothing with Conversion. Smeargle's Moody boosts drag its SpD down to -6 and never touch it for a raise, though they can certainly raise any other stats. Add in one more Conversion where Mewtwo Snatches it up (hitting Me First to become Normal type, thereby gaining STAB), and three attempts to use Stockpile which get hit with Snatch too. On turn 16, Mewtwo has to use Me First again but this time, instead of failing against Magic Room, it catches Smeargle's Spit Up and preempts it with quite a vengeance.
+6 252+ SpA Choice Specs Mewtwo Me First Spit Up (300 BP) vs. -6 252 HP / 252+ SpD Smeargle on a critical hit: 1938888-2281045 (16157400 - 19008708.3%) -- guaranteed OHKO
Dark (edited)
Absol @ Choice Band
Ability: Super Luck
EVs/Nature: Max Atk
Swords Dance
Me First
Magic Coat
blank move
-vs.-
Smeargle @ Leppa Berry
Level: 1
Ability: Moody
Magic Room
Trick-or-Treat
Conversion
Punishment
Mewtwo has the highest special attack stat of everything that can learn both Snatch and Me First, while Absol is clearly the best such user on the physical side (and in both cases they can of course raise the stats even higher with a mega stone, but simple choice items prove to be a bigger boost). Since it's already Dark, though, it doesn't need to steal Conversion to gain STAB, so in this case Snatch is pretty useless. Smeargle gets into ideal range for Punishment off of Moody boosts alone, and uses Magic Room not just for its Choice-breaking powers but also to set its Conversion type. Then, as noted above, Absol can use a bounced Trick-or-Treat to put a second type onto Smeargle, creating a double weakness so we don't have to rely on the theoretical existence of a level 1 Hoopa.
+6 252+ Atk Choice Band Absol Me First Punishment (200 BP) vs. -6 252 HP / 0 Def Smeargle on a critical hit: 2278664-2680784 (18988866.6 - 22339866.6%) -- guaranteed OHKO[/B]
Fire (edited)
Absol @ Fire Gem
Ability: Super Luck
EVs/Nature: Max Atk
Sunny Day
Snatch
Me First
Magic Coat
-vs.-
Smeargle @ Absolite
Level: 1
Ability: Moody
IVs/EVs/Nature: irrelevant
Shift Gear
Forest's Curse
Conversion
V-create
Rayquaza? Who needs that busted old thing? It doesn't even learn Snatch or Me First! Choice Band would have been nice, but there's just so much going on here that Smeargle's moveslots can't afford to spare any space for Embargo or Magic Room, and the next-best choice, Fire Gem, is a bigger boost than Absolite despite freeing up one of Absol's moves. Absol needs to Snatch a Conversion and six Shift Gears, bounce Forest's Curse, set up sun, hope the Moody boosts all go the right way, and give the V sign. For victory, of course. Shouldn't be too hard, right.
+6 252+ Atk Fire Gem Absol Me First V-create vs. -6 0 HP / 0 Def Smeargle in Sun on a critical hit: 5332068-6273024 (44433900 - 52275200%) -- guaranteed OHKO
Bug
Leavanny @ Choice Band
Ability: Swarm
Nature: Lonely
IVs: 0 HP, 0 Def
EVs: 252 Atk
Me First
Magic Coat
Swords Dance
Substitute
-vs.-
Smeargle @ Leppa Berry
Level: 5
Ability: Moody
Nature: Lonely
IVs: 0 Def
EVs: 252 Atk
Embargo
Conversion
Forest's Curse
Megahorn
Smeargle can afford to go as high as level 5 while staying at the key 7 Defense, which will be necessary this time. As will the Leppa Berry, amazingly enough. Start with Me First/Embargo as usual, then Smeargle uses Conversion to become Dark and has Forest's Curse bounced back at it to become Dark/Grass. Smeargle's first three Moody boosts are all +Atk, and now comes perhaps the most monumental task ever faced by a level 5: Leavanny needs to get into Swarm range, and the only way to do it is for Smeargle to wear it down with its incredibly weak Megahorn.
+6 252+ Atk Smeargle Megahorn vs. 0 HP / 0- Def Leavanny on a critical hit: 10-14 (3.8 - 5.3%) -- possibly the worst move ever
So even assuming max criticals every time, Megahorn's paltry supply of 8 PP is only enough for 112 damage, dropping Leavanny to 148/260. It needs to be no higher than 86 HP left, but at this point a 65HP Substitute will neatly drop to 83, just within Swarm range. Meanwhile, Leavanny has easily maxed out its attack with Swords Dance, and the process hasn't taken so long as to leave Moody with no choice but to start raising defense, so Smeargle can still be at -6 here. After the next Embargo wears off, Smeargle uses Megahorn again (which it can only do because of the Leppa Berry PP refill) , only to get brutally sniped.
+6 252+ Atk Choice Band Swarm Leavanny Me First Megahorn vs. -6 0 HP / 0- Def Smeargle on a critical hit: 3487404-4102828 (17437020 - 20514140%) -- guaranteed OHKO
Steel
Aegislash @ Steel Gem
Ability: Stance Change
Nature: Brave
IVs: 0 Spe
EVs: 252 Atk
Swords Dance
Rock Smash
Gyro Ball
blank move
-vs.-
Amaura @ Focus Band
Level: 3
Ability: Refrigerate
Nature: Hasty
IVs: 0 Def
EVs: 252 Spe
Thunder Wave
Icy Wind
Rock Polish
blank move
The only way for either of these two to put -Def on Amaura is with Rock Smash, which means Amaura can't afford to hold a scarf: it needs six straight Focus Band saves while the stat drop hits every time. Neither of them have access to Magic Room, Embargo, or even Trick/Switcheroo, so there's no way to work a Choice Band into all the setup that needs doing since 1v1 precludes having it Baton Passed in from someone else. That leaves Steel Gem as the next best choice, edging out Life Orb by 377 damage. The final speeds after all the adjustment are 7 for Aegislash and 44 for Amaura, good enough to hit the 6:1 ratio that results in full power.
+6 252+ Atk Steel Gem Aegislash-Blade Gyro Ball (150 BP) vs. -6 0 HP / 0- Def Amaura on a critical hit: 2195380-2582808 (12196555.5 - 14348933.3%) -- guaranteed OHKO
Ground
Rhyperior @ Choice Band
Ability: Reckless
max Atk
Magnitude
blank move
blank move
blank move
-vs.-
Aron @ Aggronite
Level: 1
Ability: Sturdy
Body Slam
Swagger
Superpower
Dig
Rhyperior leads with Magnitude, which would obviously be overkill if not for Sturdy. Aron fights back with Body Slam and gets the paralyze, and then Rhyperior just stays fully paralyzed forever while Aron sets up singlehandedly: 3 Swaggers to max out Rhyperior's Attack, 6 Superpowers to kill off its own Defense, then go underground with Dig. The following turn, Rhyperior fights through both paralysis and confusion to set off a Magnitude 10, and Sturdy won't save Aron this time, no matter how much it feels like a Fissure.
+6 252+ Atk Choice Band Rhyperior Magnitude (300 BP) vs. -6 0 HP / 0 Def Aron on a critical hit: 4811800-5660944 (40098333.3 - 47174533.3%) -- guaranteed OHKO
And an exact tie with that from a different type:
Fighting
Conkeldurr @ Choice Band
Ability: Guts
max Atk
Reversal
blank move
blank move
blank move
-vs.-
Aron @ Aggronite
Level: 1
Ability: Sturdy
Body Slam
Swagger
Superpower
Endeavor
Similar thing here: Reversal once, take a Body Slam paralyze, and get FP for a while. Set up the appropriate stats with Aron, Endeavor Conkeldurr straight to 1 HP (the Body Slam/Superpower setup moves only dealt 1 damage each), and let it fire off max power Reversal.
+6 252+ Atk Choice Band Guts Conkeldurr Reversal (200 BP) vs. -6 0 HP / 0 Def Aron on a critical hit: 4811800-5660944 (40098333.3 - 47174533.3%) -- guaranteed OHKO
Ghost
Mewtwo @ Choice Specs
Ability: Pressure
max SpA
Me First
Magic Coat
Psych Up
Thunder Wave
-vs.-
Smeargle @ Mewtwonite Y
Level: 1
Ability: Moody
min SpD
Magic Room
Trick-or-Treat
Conversion
Hex
This is actually pretty fast to set up:
Turn 1 - Mewtwo Me First (fails), Smeargle Magic Room. Smeargle +2 SpA, -1 SpD.
Turn 2 - Mewtwo Magic Coat (fails), Smeargle Conversion. Smeargle is now Psychic type, +4 SpA, -2 SpD.
Turn 3 - Mewtwo Magic Coat, Smeargle Trick-or-Treat. Smeargle is now Psychic/Ghost type, +6 SpA, -3 SpD
Turn 4 - Mewtwo Psych Up, acquiring the +6 SpA for itself. Smeargle Trick-or-Treat. Mewtwo is now Psychic/Ghost type. Smeargle -4 SpD.
Turn 5 - Mewtwo Thunder Wave, Smeargle Trick-or-Treat (fails). Smeargle -5 SpD. Magic Room wears off, and Mewtwo goes back to being Choice locked into Me First.
Turn 6 - Mewtwo Me First, preempting Smeargle's Hex.
+6 252+ SpA Choice Specs Mewtwo Me First Hex (130 BP) vs. -5 0 HP / 0 SpD Smeargle on a critical hit: 3360736-3953812 (28006133.3 - 32948433.3%) -- guaranteed OHKO
Dragon
Mewtwo @ Choice Specs
Ability: Pressure
max SpA
Mimic
Me First
Psych Up
Snatch
-vs.-
Smeargle @ Soul Dew
Level: 1
Ability: Moody
Roar of Time
Embargo
Conversion
blank move
Yeah, we all know how this works by now. The only real snag this time is that Mewtwo's movepool, expansive as it might be, does not contain any Dragon-type moves whatsoever (the only other type it misses is Fairy). Furthermore, Mew gets Reflect Type, but Mewtwo does not, and it's not callable with Snatch. The only way to transfer Dragon type to Mewtwo is by having Smeargle let loose a 1-damage Roar of Time, have Mewtwo mimic that to put it in slot 1 (it'll never actually click that move), and then later on Snatch a Conversion of its own.
+6 252+ SpA Choice Specs Mewtwo Me First Roar of Time vs. -6 0 HP / 0 SpD Smeargle on a critical hit: 1938890-2281050 (16157416.6 - 19008750%) -- guaranteed OHKO
Grass
Venusaur @ Choice Specs
Ability: Overgrow
max SpA
Frenzy Plant
Grassy Terrain
Growth
blank move
-vs.-
Binacle @ Focus Band
Level: 1
Ability: Tough Claws
Embargo
Shell Smash
Endeavor
blank move
Sceptile would be better, of course, other than the pretty glaring omission that Sceptile doesn't have any way of racking up SpA boosts at all (not even using Mimic to acquire Binacle's Shell Smash, because Mimic is incompatible with Grassy Terrain). Binacle doesn't exactly need the Focus Band here, since Frenzy Plant can miss and it's not counting on hitting to get any stat boosts, but it's nice to have.
+6 252+ SpA Choice Specs Overgrow Venusaur Frenzy Plant vs. -6 0 HP / 0 SpD Binacle in Grassy Terrain on a critical hit: 4268164-5021376 (35568033.3 - 41844800%) -- guaranteed OHKO
Fairy
Sylveon @ Fairy Gem
Ability: Pixilate
max SpA
Sleep Talk
Calm Mind
Rest
Trump Card
-vs.-
Deino @ Claw Fossil
Level: 1
Ability: Hustle
Earth Power
Psych Up
Spite
blank move
This one's a bit of an oddball. First off, neither Deino nor Scraggy can learn Embargo for some strange reason, so Choice Specs are out. Deino needs to use Earth Power for six SpD drops, then Psych Up those stats to itself, before Sylveon starts using any Calm Minds. Sylveon actually wants to waste Sleep Talk PP while it's still awake, and once Deino has crippled itself with Psych Up, the string of six Calm Minds can begin. After Sylveon gets down to 1 PP on Sleep Talk, it should use Rest to wipe away the (obviously crippling) damage from the Earth Powers, then use Sleep Talk to call Trump Card. The result of this is that even though this is the first time Trump Card is being used, it's looking at Sleep Talk's PP for it, giving the full 200 power. Ah, ruleset restrictions. It's like you were never even there.
+6 252+ SpA Fairy Gem Pixilate Sylveon Trump Card (200 BP) vs. -6 0 HP / 0 SpD Deino on a critical hit: 3040792-3577408 (25339933.3 - 29811733.3%) -- guaranteed OHKO
Ice
Glalie @ Glalitite
Ability: Moody -> Refrigerate
max Atk
Leer
Explosion
blank move
blank move
-vs.-
Hoppip @ Air Balloon
Level: 1
Ability: Infiltrator
Splash
blank move
blank move
blank move
Moody sure is great for setting up free boosts, isn't it?
+6 252+ Atk Refrigerate Mega Glalie Explosion vs. -6 0 HP / 0 Def Hoppip on a critical hit: 3107628-3656032 (28251163.6 - 33236654.5%) -- guaranteed OHKO
Flying
Pinsir @ Pinsirite
Ability: Mold Breaker -> Aerilate
max Atk
Swords Dance
Me First
blank move
blank move
-vs.-
Smeargle @ Scizorite
Level: 1
Ability: Moody
Forest's Curse
Reflect Type
Explosion
blank move
Funny how that typing works out, huh. The other types weren't so cooperative to stuff like this.
+6 252+ Atk Aerilate Mega Pinsir Me First Explosion vs. -6 0 HP / 0 Def Smeargle on a critical hit: 5632060-6625960 (46933833.3 - 55216333.3%) -- guaranteed OHKO
Poison
Gengar @ Choice Specs
Ability: Levitate
max SpA
Shadow Ball
Psych Up
Toxic
Venoshock
-vs.-
Cottonee @ Focus Band
Level: 1
Ability: Prankster
Growth
Switcheroo
Leech Seed
blank move
It's more complicated than Embargo or Magic Room loops, but this will work in a pinch. Yet again, running Shadow Ball into Focus Band is the only way Gengar can get the stat drops it needs. Furthermore, it has no innate way of boosting its own SpA. After six turns of Growth/Shadow Ball, turn 7 sees Cottonee switch the items with Switcheroo, but it still has to get a seventh Focus Band hit since Gengar was still choice locked at the beginning of the turn. Now Cottonee has the Specs, and Gengar is free to switch moves: Psych Up lets it copy Cottonee's +6 SpA/-6 SpD, but before that happens, a Prankster Switcheroo means Gengar is now choice-locked into Psych Up. That's a harmless move to be executing repeatedly, so Gengar keeps using Psych Up for a couple more turns while Cottonee puts up Leech Seed (which restores it to full health) and uses Switcheroo to take the Specs back. The remaining turns go Switcheroo-Toxic (so now Cottonee is poisoned), Switcheroo-Toxic again (Cottonee has the Specs, so Gengar is free to switch moves), and Switcheroo-Venoshock. Prankster means that Gengar gets the power boost from Specs back in the first half of the turn, before it uses its move in the second half.
+6 252+ SpA Choice Specs Gengar Venoshock (130 BP) vs. -6 0 HP / 0 SpD Cottonee on a critical hit: 1974844-2323348 (17953127.2 - 21121345.4%) -- guaranteed OHKO
Rock
Rampardos @ no item
Ability: Mold Breaker
max Atk
Curse
Leer
Thief
Head Smash
-vs.-
Ledyba @ Choice Band
Level: 1
Ability: Swarm
Endure
blank move
blank move
blank move
Here's another way to work around Choice setup. Ledyba of course does nothing but spam Endure, which has 16 PP. Meanwhile, Rampardos gets a full set of Curses and Leers, with 4 PP left on Endure. There have been some failures in the main time, and probably some double-endure hits that never got used up, but now the 13th use needs to hit to protect Ledyba from Thief, allowing Rampardos to steal the Choice Band and lock itself into a nice, big Head Smash. Endure #14 should fail, of course.
+6 252+ Atk Choice Band Rampardos Head Smash vs. -6 0 HP / 0 Def Ledyba on a critical hit: 2723992-3204700 (24763563.6 - 29133636.3%) -- guaranteed OHKO
Water
Mewtwo @ Choice Specs
Ability: Pressure
max SpA
Rain Dance
Me First
Psych Up
Snatch
-vs.-
Smeargle @ Blue Orb
Level: 1
Ability: Moody
V-create
Conversion
Embargo
Hydro Cannon
Once again, the main weather types offer enough multipliers that it makes sense to use Smeargle to help chase them all, rather than pick on a mere double weakness. V-create, out of place as it may be in this scenario, can actually help drive Smeargle's SpD down even faster, in addition to being the move that sets the Conversion type. After all, you can never have too much V-create.
+6 252+ SpA Choice Specs Mewtwo Me First Hydro Cannon vs. -6 0 HP / 0 SpD Smeargle in Rain on a critical hit: 2908338-3421574 (24236150 - 28513116.6%) -- guaranteed OHKO
Electric (edit 4!)
Magnezone @ Life Orb
Ability: Analytic
max SpA
Electro Ball
Metal Sound
Charge Beam
Electric Terrain
-vs.-
Mantyke @ Quick Claw
Level: 1
Ability: Water Absorb
Endure
Splash
blank move
blank move
Well, at least Electro Ball doesn't require so much maneuvering to make work the way Gyro Ball does in the presence of a 90+ level advantage. None of the Water/Flying candidates have any of the moves that would allow Choice setup. Furthermore, Magnezone has no way of building SpA other than Charge Beam boosts, so Mantyke has to Endure those, and that means Electric Gem isn't an option (since the main event will have to be the seventh Electric attack used, not the first). Once all the stat boosts are in place, Magnezone sets Electric Terrain, then next turn Mantyke gets its Quick Claw to fire on Splash. Obviously that doesn't deal any damage, but it does trip the "opponent went first this turn" flag that allows Magnezone to get its Analytic boost despite being far faster than the enemy, just as Electro Ball requires.
+6 252+ SpA Life Orb Analytic Magnezone Electro Ball (150 BP) vs. -6 0 HP / 0 SpD Mantyke in Electric Terrain on a critical hit: 3850365-4529845 (35003318.1 - 41180409%) -- guaranteed OHKO
Forget all that. Double weaknesses are overrated anyway.
Espeon @ Life Orb
Ability: Synchronize
Zap Cannon
Mimic
Skill Swap
Stored Power
-vs.-
Smeargle @ Quick Claw
Level: 1
Ability: Moody
Waterfall
Conversion
Electric Terrain
Electrify
This is another one of those cases where there's so much going on that we can't afford a spare slot for managing Choice Specs. Espeon leads with Skill Swap to take Moody for itself, Smeargle uses Conversion, and keeps spamming Conversion while Espeon uses Mimic to gain Conversion, uses all five Conversion PP that it gets, and uses all eight Zap Cannon PP (they all miss, of course). Espeon has now had 15 turns of Moody boosts, but it doesn't have the PP to keep going, so Smeargle helps out with 24 straight Quick Claw Waterfalls, all of which get the flinch. Espeon is now at 39 boosts, close enough to the finish line, so it keeps Skill Swapping back and forth to let everyone take turns getting Moody. This is enough to bring Espeon to +41 (it's impossible to end a Moody turn at +42, and the move slots are so jam-packed that neither one can afford to spare anything to get the last boost), and drop Smeargle to -6 SpD. Toward the end, Smeargle lays Electric Terrain, and gets the jump on Stored Power with a Quick Claw Electrify.
+6 252+ SpA Life Orb Espeon Stored Power (840 BP) vs. -6 0 HP / 0 SpD Smeargle on a critical hit: 5528722-6504379 (46072683.3 - 54203158.3%) -- guaranteed OHKO
...hang on, why limit ourselves to innate users of Stored Power with its limited distribution? Maybe Magnezone was onto something.
Magnezone @ Electric Gem
Ability: Analytic
max SpA
Mimic
Psych Up
Magic Coat
Iron Defense
-vs.-
Smeargle @ Quick Claw
Level: 1
Ability: Moody
min SpD
Soak
Electric Terrain
Electrify
Stored Power
Unlike either Espeon or Latios, Magnezone doesn't need to spend a move slot to gain STAB, and it can put the ability slot to use for a change. The boost levels are really finicky here, so Smeargle absolutely needs a nature that gives it a stat of 4 in SpD: that means it reaches an effective stat of 1 after just -3, instead of having to go further. Anyway, Magnezone uses Mimic to acquire Stored Power from Smeargle, and Magic Coat to bounce Smeargle's Soak back at it, setting its type and wasting time while Smeargle pulls in boosts from Moody. After wasting enough time, Smeargle can be at -5 Def, +3 SpD, +6 everything else in time for Magnezone to copy those stats with Psych Up. Magnezone then needs to fix its Defense with Iron Defense, while Smeargle's Moody boosts rearrange themselves just right...
At the end of the Psych Up turn: -3 Def, +2 SpD
Iron Defense turn 1: Magnezone -3 Def; Smeargle -1 Def, +1 SpD
Iron Defense turn 2: Magnezone -1 Def; Smeargle +1 Def, 0 SpD
Iron Defense turn 3: Magnezone +1 Def; Smeargle +3 Def, -1 SpD
Iron Defense turn 4: Magnezone +3 Def; Smeargle +5 Def, -2 SpD
Iron Defense turn 5: Magnezone +5 Def; Smeargle +6 Def, +5 Atk (or any other random stat)
Iron Defense turn 6: Magnezone +6 Def; Smeargle +6 Atk, -3 SpD (Special Defense is now 1 point)
This gives Magnezone a total of 39 out of a possible 42 boost levels, which looks as good as it's possible to achieve with Psych Up plus one other boosting move from Magnezone's move pool; Smeargle obviously can't afford to spare a slot on Swagger to help out in that regard. Then on the following turn, before Moody has no choice but to lift SpD back up, the Quick Claw Electrify strikes, playing right into Analytic.
+6 252+ SpA Electric Gem Analytic Magnezone Stored Power (800 BP) vs. -3 0 HP / 0- SpD Smeargle in Electric Terrain on a critical hit: 10269162-12081368 (85576350 - 100678066.6%) -- guaranteed OHKO
That would be all well and good, except that it occurred to me the above set is actually illegal. Magnemite can only get Mimic from G3, and Analytic is a hidden ability so it can't be swapped on. Back to the drawing board.
Obviously, just taking away Analytic makes it legal and gives a figure in the 9-millions. But as I was searching for replacements, the most promising one was one that doesn't appear in Magnezone's movepool at all. It can learn Charge Beam, Discharge, and even Wild Charge, but not just plan Charge, which is dumb. As a 100% boost, it's bigger than any other multiplier that fits into one slot, so even if the stat has to drop below Magnezone's, getting the bigger multiplier could make up for it. I looked through all the possible candidates for holding both Mimic and Charge, and apart from another Smeargle, they all either lacked a way of acquiring Smeargle's boosts (such as Skill Swap or Psych Up), or a way of bouncing back Soak, which would have forced Smeargle to rely on Conversion + dummy move when its moveslots are already overloaded and can't afford to spare one more.
But what if Mimic wasn't used to acquire Stored Power...what if it got Charge? That brings us back to something resembling the Espeon scenario, but Mimic was already devoted to grabbing Conversion there. That'll mean giving up something as big as STAB, but Charge is still bigger, so just maybe...yes, version 4 can work with that.
Latias @ Soul Dew
Ability: Levitate
max SpA
Role Play
Mimic
Magic Coat
Stored Power
-vs.-
Smeargle @ Quick Claw
Level: 1
Ability: Moody
Soak
Charge
Electric Terrain
Electrify
Yes, Latias does seem like a suboptimal choice for offense, particularly when Latios exists. But Latios doesn't work here, because of a move he doesn't get: Role Play. Sure, Latios does get Psych Up, but what makes Role Play superior here is the fact that neither one of them can get the Electric Terrain boost unless they lose Levitate.
Latias uses Role Play to acquire Moody, Mimic to acquire Charge, and Magic Coat to bounce back Soak and make Smeargle acquire the Water typing. You should be familiar with the process by now. But even though both sides have Moody ticking up at the same rate, Latias can have them distributed to reach +41, while Smeargle can go for the bottom in SpD and have two other stats wobble back and forth between +6 and +5, essentially a "holding pattern" where its own Moody produces no net change after a while. When Latias is missing only a SpD boost, Charge on the next to last turn can alleviate that, move it to a drop in any other stat except SpA, and set up the massive confluence of multipliers.
+6 252+ SpA Soul Dew Latias Charge Stored Power (840 BP) vs. -6 0 HP / 0 SpD Smeargle in Electric Terrain on a critical hit: 11335470-13335848 (94462250 - 111132066.6%) -- guaranteed OHKO
Psychic (edit)
Espeon @ Choice Specs
Ability: Synchronize
EVs/Nature: Max SpA
Psych Up
Focus Energy
Shadow Ball
Stored Power
-vs.-
Croagunk @ Focus Band
Level: 1
Ability: Anticipation
IVs/EVs/Nature: irrelevant
Acupressure
Embargo
Meditate
Nasty Plot
Espeon starts by running a +0 Stored Power into Croagunk's bare Focus Band, while Croagunk puts up Embargo to lift the Choice lock for a while. Then Espeon starts spamming Focus Energy just to waste time, and Croagunk builds up all of its stats with Acupressure. Every fifth turn will be Embargo/Stored Power, which must trigger the Focus Band every time, while Croagunk reestablishes Embargo. Once all stats are maxed out, Espeon copies the +6 everything for itself with Psych Up. Then comes the tricky part: Croagunk had to be at +6 SpD for Espeon to copy it, but needs to go down to -6 for maximum damage. That means twelve Shadow Balls, all of which have to hit the Focus Band yet again, and all of which have to get the SpD drop. Finally, the next time Embargo ends (giving the Choice Specs back their damage boost), after this astonishingly unlikely run of good luck on Croagunk's end, let it run out and let it rip.
+6 252+ SpA Choice Specs Espeon Stored Power (860 BP) vs. -6 0 HP / 0 SpD Croagunk on a critical hit: 13064320-15369792 (108869333.3 - 128081600%) -- guaranteed OHKO
That's a higher figure than any other type, but it left Croagunk disappointed. How could it live with being the biggest laughing stock in all of Pokemon, the wimpiest wimp left to take the hardest hit in all of 1v1 battling for all to see? What better way to motivate it to try harder. To be the attacker, not the punching bag. To grow up big and strong and...with numbers like those, you'd swear it'd have to go "super saiyan". No matter how strong it grows, there's the problem that its Special Attack stat won't be able to get anywhere near Espeon's. But what can it do instead?
Toxicroak @ Choice Specs
Ability: Anticipation
max SpA
Meditate
Snatch
Acupressure
Me First
-vs.-
Smeargle @ Quick Claw
Level: 1
Ability: Moody
Embargo
Reflect Type
Conversion
Stored Power
Toxicroak begins by shuddering, because obviously it still has flashbacks of what a move like Stored Power can do. The only ways Smeargle can ever become double weak to Psychic are with Transform or Reflect Type, both of which only work if the opponent is specifically either Croagunk or Toxicroak, so here we are. But first, Smeargle (who revels in its ability to run so many obscure sets that set it up as a punching bag, a role it's embraced over the type chart) chimes in with a Quick Claw Embargo, which prevents Toxicroak from ever being locked into anything and speeds things up by not making Toxicroak use Me First every fifth turn. 21 turns can max out Acupressure, and after all that's done, Smeargle tries to brace itself for the incoming impact by setting its type to Dark with Conversion, but that gets Snatched away, causing Toxicroak to become Psychic/Fighting. Then on turn 26, Toxicroak finally unleashes the Me First-boosted move it's been building up to for so many years.
+6 252+ SpA Choice Specs Toxicroak Me First Stored Power (860 BP) vs. -6 0 HP / 0 SpD Smeargle on a critical hit: 14821704-17437300 (123514200 - 145310833.3%) -- guaranteed OHKO
Just for completeness, Delcatty's Normalize Stored Power falls short of Mewtwo's Spit Up in the Normal category by the surprisingly close margin of about 50,000 damage. This is because of its poor attacking stat in comparison to Mewtwo, and the fact that it can only use the move by way of Mimic or Copycat; if Delcatty could get a Me First Stored Power, that would be enough to put it in first place for Normal, and to bring that type out of the cellar for that matter. Smeargle as the attacker can use Me First Normalize Stored Power against Skitty, but its Special Attack is even worse, so that it falls short of Delcatty by an even closer amount, around 10,000 damage. Stored Power may have the highest power of any move, but that doesn't mean it's a panacea for every scenario it can be theoretically retyped to. Two out of three ain't bad, at least.
So if I didn't miss anything, and if it's all accurate, that leaves the relative order of all the types in 1v1 as follows:
1. Psychic | Toxicroak vs. Smeargle | Stored Power | 17,437,300
2. Electric | Latias vs. Smeargle | Stored Power | 13,335,848
3. Flying | Pinsir vs. Smeargle | Explosion | 6,625,960
4. Fire | Absol vs. Smeargle | V-create | 6,273,024
T5. Ground | Rhyperior vs. Aron | Magnitude | 5,660,944
T5. Fighting | Conkeldurr vs. Aron | Reversal | 5,660,944
7. Dark | Absol vs. Smeargle | Punishment | 5,361,568
8. Grass | Venusaur vs. Binacle | Frenzy Plant | 5,021,376
9. Bug | Leavanny vs. Smeargle | Megahorn | 4,102,828
10. Ghost | Mewtwo vs. Smeargle | Hex | 3,953,812
11. Ice | Glalie vs. Hoppip | Explosion | 3,656,032
12. Fairy | Sylveon vs. Deino | Trump Card | 3,577,408
13. Water | Mewtwo vs. Smeargle | Hydro Cannon | 3,421,574
14. Rock | Rampardos vs. Ledyba | Head Smash | 3,204,700
15. Steel | Aegislash vs. Amaura | Gyro Ball | 2,582,808
16. Poison | Gengar vs. Cottonee | Venoshock | 2,323,348
17. Dragon | Mewtwo vs. Smeargle | Roar of Time | 2,281,050
18. Normal | Mewtwo vs. Smeargle | Spit Up | 2,281,045
