Godlike:
Odd Eye (ShF2) vs. Melfice (G2): Sure, I'll bite.
Barbariccia (FF4) vs. Nailah (FE10): I think Nailah has a better shot here than others, her sky-high accuracy means she actually hits through spin pretty well. But... Weak is surely still turn 1, and if the followup poke also lands (which it should over half the time), Valvalis still takes this without much issue.
Velius (FFT) vs. Elyon (BoF5): Goes first, and certainly isn't killing in less than 2 turns, since he has gravity and can quarter Velius's HP on turn 1.
Tir McDohl (S1) vs. Chris Lightfellow (S3): Faster.
Heavy:
Summoner (FF5) vs. Tidus (FFX): Quick Hit x4 is 84% damage, Summoner has 0.78 pdur, and isn't getting a turn before Tidus's fourth.
Nel Zelpher (SO3) vs. Therion (OT): Therion can't kill anything before turn 3, Nel freezes him before that.
Asellus (SaGa) vs. Celica (FE:SoV): Goes first, 2HKOs, needs to dodge a counter since otherwise Celica 2HKOs first, but with all her nonsense she probably does.
Middle:
Tifa Lockhart (FF7) vs. Leehalt Alceste (WA3): I have a lot of respect for Rule of Vengeance these days, so Tifa will probably die if she attacks. But she doesn't need to do that, she sits there until she gets a really good limit (L2 is enough, surely) and one-shots Leehalt.
Amarant Coral (FF9) vs. Bowser (SMRPG): Assuming Bowser goes for turn 1 Fear, Amarant kills in four attacks (one full + three halved). Bowser kills in three (Terrorize + Physical x 1.5 x 2). So that's a win unless Amarant can muscle out some extra damage/healing somewhere, perhaps in an attempt to wait out Fear. Chakra is a thought. In fact... yeah that probably works? Bowser does 13% to Amarant with Terrorize, and 37.3% (56% with fear) with his physical, while Amarant heals for 40%. So Terrorize + three physicals is 181%, while Chakra almost heals that... not quite, but enough that Bowser will miss with fear or run out of MP eventually. And... yeah Amarant can also apply regen on turn 1 to put a further dent, and as a bonus it gives him Auto-Life. This match is probably his.
Albel Nox (SO3) vs. MOMO (XSs): Not thinking about this too hard.
Light:
Ricardo Banderas (XG) vs. Labyrinthia Wordsworth (WA:XF): Barely faster, so she 2HKOs first. Though, with Rico's accuracy and Weapon Guard, Rico probably misses one of his first two attacks anyway.
Cotton (SaGa) vs. Zhuzhen Liu (SH1): Zhuzhen needs almost all of his MP to win this, I think, but win it he does.
Benedict (TriStrat) vs. Millich Oppenheimer (Suikos): Hey, Milich is distinctly a 3HKO machine, not a 4HKO machine! Benedict, meanwhile, might 4HKO on a good day, and Milich is tanky so this is not a good day.
Boco (FFT) vs. Annette (FE3H): Random's strategy makes sense: Annette can kill with Wind + Wind counter + Dust, so she heal-locks with Wind which criticals at some point. ... except that critical doesn't actually kill? But... Boco is below average FFT speed which means Annette will doubleturn him eventually, and when she does she can finally use melee attacks since she can endure a counter and 2HKO with Lightning Axe -> Dust.