Godlike:
Shania (SH:FtNW) vs. Citan Uzuki (XG): Mathed this out in chat. Citan can use haste then get three attacks before Shania's second turn, one against her unbuffed human form and two against buffed Tirawa. This does about 50% + 20% + 20% = 90%, not enough. Shania's strategy is to buff with Sanlittobell on her first turn then KO with Shining Zephyr + Sun Flare on her second.
Edelgard von Hresvelg (FE3H) vs. Mewtwo (PKMN): Goes first, uses Barrier, then can survive anything Edelgard does. If you take her crits as ignoring barrier (which... yeah I probably would, I suppose?) that gives her a glimmer of a chance but still not really, a crit won't OHKO even then.
Melfice (G2) vs. Barbariccia (FF4): His attacks are ITE, hers aren't.
Elyon (BoF5) vs. Tir McDohl (S1): Pretty close, could be argued. Tir certainly 2HKOs to me (Elyon's absolute defence is the only reason he isn't OHKOed), and as far as I'm concerned gets his second turn before Elyon does because Tir's speed actually does something on turn 2. That said, I don't think this call particularly matters, just means Elyon has to settle for two clone attacks instead of two attacks of his own, which is only a very small damage cut. Elyon does 1.47x Tir's HP with two turns of his own (so... slightly less with the clones, like 1.4x probably). Buuut that's physical, and Tir has 40% evade, so I think he likely takes this. (Magic damage isn't an option since Tir halves that.)
Heavy:
Clarissa Arwin (WA:XF) vs. Rufus (VP2): Faster, Sacrifice.
Geno (SMRPG) vs. Lady Elmina Harken (WA:ACF): So Geno's strategy is to Boost, then 2HKO. I'm inclined to say Geno goes first, then Harken immediately doubles (again, ACF speed does something on turn 2, SMRPG does not) but honestly that's pretty great for Geno since it means Harken's first two attacks are at full HP facing boosted defence and the third is somewhere below half. If Geno can do the right amount of damage, I think he might barely pull this out IF Geno Boost is seen as halving the ITD damage boost of Maximum Risk. (If it doesn't, he's toast.)
Overall, laying it out like this, I think I have to vote for Harken. There's a chance she goes first, at which point her opening turn does enough damage for her to complete the 3HKO even through boost. There's an argument Maximum Risk pierces boost. And there's a chance that Geno can't do exactly the right amount of damage needed, even if the other two calls fall his way (I suspect he can, admittedly, but I'm not sure).
@Tide: The difference between Geno and Lyon here is that Geno only does like 60% with his best damage while Lyon does something closer to 85%, letting Lyon chip with something really weak while Geno has open himself up to one pretty substantial Max Risk.
Hildegarde Valentine (SH:FtNW) vs. Summoner (FF5): Faster, Grand Slam.
Nel Zelpher (SO3) vs. Asellus (SaGa): Ice Daggers is 57% freeze, but that drops to 31% against Asellus's evade + Deflect, so Nel wins with freeze on turn 3, and is faster. Asellus can just 2HKO her first though. Can Nel just spam Healing in response to that, hoping to run Asellus out of MP? It really depends if you see Healing slow enough to let Asellus double her at some point. I don't think I do. Asellus's other hope is that she will doubleturn Nel after using Mystic Change which... really depends on Nel's speed past turn 1, which Dhyer says is untested. So... do I still consider Nel fast past turn 1? ..... yeah, probably. Very much could be argued.
Middle:
Jude Maverick (WA4) vs. Anastasia Romanov (SH2): Jude can block a status but it comes at a pretty serious stat hit, reducing him to a 3HKO. That said, it looks like he barely 3-2's even before Anastasia recoil is considered? Might have made a math error.
Stocke (RH) vs. Jessica de Alkirk (L:SSSC): RH paralyze functions as silence as well, so there's certainly a case for a blocker there but I dunno how I feel about that.
Tifa Lockhart (FF7) vs. Amarant Coral (FF9): Gets a good limit.
MOMO Mizrahi (XSs) vs. Kesaran Pasaran (WA4): Kesaran doesn't quite instant double and I think MOMO just OHKOs him.
Light:
Marianne (FE3H) vs. Squire (FFT): Marianne has a 4HKO (Iron Lance Frozen Lance x3, finish with Silver Lance) and Renewal to regain 20% HP per turn. Squire does 39%, and goes first, which is a kill on turn 5, not good enough. Except... wait. Squire gets two COUNTER TACKLES which do the needed extra damage, wtf. So never mind, Marianne goes for Nosferatu, which actually lets her counter for non-zero damage. And... yeah that's surely enough, it actually does more damage than Frozen Lance due to this, by a notable amount, and gives her a little push of extra healing. The only issue is that it may well get her doubled. And... that's close, but I don't think so offhand, Squire is only barely above average.
Hubert (FE3H) vs. Queen (S3): Banshee.
Labyrinthia Wordsworth (WA:XF) vs. Zhuzhen Liu (SH1): I guess Zhuzhen can heal until a double and then use the resulting initiative to 3HKO? He... only barely 3HKOs with Thunder Roar though (Labby resists his best). That leaves him MP to heal 10 times. Does he doubleturn within 10 turns? Yeah, surely. And he has the SP for this, too.
Millich Oppenheimer (Suikos) vs. Annette Fantine Dominic (FE3H): Huh yeah, Milich definitely worse in the new (and by new I mean 2016) stat topic. Depressingly so. Ah well.
