Godlike
Ash Lambert (Vandal Hearts) vs Kraken (Final Fantasy III): Vandalier's not really legal to me any more... but Ash was nommed in Godlike, so I might as well vote on him that way to make him not boring. *checks stat topic* And we don't even have damage numbers for VH, great. Kraken will use Blizzara + Blind, that heal-locks and sometimes statuses, probably good enough. Obvious desire to tiebreak for the one with proper numbers, why is that the plotless FF3DS boss.
Mattias (Octopath Traveler) vs Gadgeteer (Wild ARMs XF): My memory is that Exploder Gem +1's are really too expensive to be legal, but the Ice Gem +1's should be fine, and those.. actually suffice. Since Gadgeteer is above average speed, she should get a second turn in the same "round" once her speed is doubled, then two more the next round, which is a total multiplier of 1.3 + 2*3 = 7.3x Ice Gem damage, which is over 6PCHP. That should be enough.
Yokai (Bravely Second: End Layer) vs Mewtwo (Pokémon): Physical instant death? uh oh.
Heavy
Tiki (Fire Emblem: Shadow Dragon) vs Adelbert Steiner (Final Fanasy IX): Steiner is both more durable and more damaging, and avoids counters. Goes second, but surely he kills in one less hit... also has some evade.
Erik (Dragon Quest XI) vs Nel Zelpher (Star Ocean: Till the End of Time): If DQ11's length were more reasonable I'd be able to vote on this by now. Alas.
Camilla (Fire Emblem Fates) vs Umi (Cthulhu Saves the World): Blind Strike seems pretty legit, don't see any reason to disagree with Random.
Rabbid Luigi (Mario + Rabbids Kingdom Battle) vs Chemist (Final Fantasy V): Rabbid Luigi tosses away all his weapons, and dashes into Chemist over and over healing until Chemist runs out of items, because it's funnier that way and Rabbid Luigi lives for that. (Hm, actually, level-boosting means there's a chance Chemist could break past this eventually. FINE, he uses the stone-inflicting yo-yo, happy?)
Middle
Edge Maverick (Star Ocean The Last Hope) vs Lich (Final Fantasy): Edge's ice defence doesn't do much good since it makes him fire-weak, he's still 3HKOed... still, he takes 36% while his healing restores 40% (with occasional doubles), so he can make some headway! Otherwise, block paralysis. Slow will cut his damage (I'd call it no combos) but eh he can't... really lose, he has ways to get MP back even, and his healing is so ridiculously cheap.
Setsuna (I Am Setsuna) vs Sylveon (Pokémon): Sylveon can't... really break past the healing? May take a while, but momentum seems good for fights like this.
Finn (Child of Light) vs Vivi Ornitier (Final Fantasy IX): Yeah surely.
Light
Hubert von Vestra (Fire Emblem: Three Houses) vs Chu-Chu (Xenogears): Probably, Chu-Chu is pretty terrible.
Lauren (Cosmic Star Heroine) vs Rude (Final Fantasy VII): Lauren vs boss seems bad for her.