Godlike
Lady (Shadow Hearts: From the New World) vs Gau (Final Fantasy VI): Sweet merciful crap.
Psaro (Dragon Quest IV) vs Sanctuary Keeper (Final Fantasy X): Sanctuary Keeper can run Protect/Regen and spam Curaga to completely shut down the forms without both (a) double-acting and (b) dispel or good magic damage. Which is... just form 7. And I'm pretty sure SK wins a slugfest going into the final round at full health.
Ryu Bateson (Breath of Fire II) vs Jade (Breath of Fire): The HP.
Chelle (Wild ARMs XF) vs Tir McDohl (Suikoden Series): Slightly faster, and can tank a Judgement to me, so can afford to miss.
Heavy
Raynie (Radiant Historia) vs Lawfer (Valkyrie Profile): Probably interesting if you allow Switch.
Geddoe (Suikoden III) vs Alena (Dragon Quest IV): uhh something, I imagine Alena gets two turns and Geddoe has parry, so... close. I'll think about it later. EDIT: see Super
Say’ri (Fire Emblem: Awakening) vs Edna Capone (Shadow Hearts: From the New World): Think so. Edna can't 2HKO with anything, while Say'ri kills in two turns, so Edna needs all three attacks to hit on her first turn + double on her second. Say'ri has too much evade for that.
Oerba dia Vanille (Final Fantasy XIII) vs Cloud Strife (Final Fantasy VII): Cloud needs to block Pain, but if he does... Vanille can still set up, but Cloud can hit her kinda hard in the meantime? Nah, she'll heal. Actually, POISON causes big problems for Cloud, of all things, since that doesn't trigger a limit. Vanille can just poison him then heal forever. Except WAIT, blind and poison share a blocker, whoops. So Vanille needs to set up a blitz after all. Seems... difficult but possible, but I'm open to arguments here.
Middle
Meganium (Pokémon) vs Henry (Fire Emblem: Awakening): Henry has a low 2HKO here with Bolganone, but Meganuim is faster and can use Light Screen to make that a low 4HKO (and make Nosferatu's draining terrible). Of all things, I believe Meganuim wants POISON POWDER since it doesn't trigger counters and frees up later Meganuim turns for Synthesis and refreshing Light Screen. This probably gets the jbo done, with Body Slam to finish (or Razor Leaf if you don't see Tomebreaker getting that, I'm not certain myself). Vengeance is interesting since it can add up to ~10 healing to Nosferatu draining, which actually does let Henry turtle against poison to some extent, but I'm pretty skeptical it lets him win since by the time it's useful, he's very close to death range.
Stocke (Radiant Historia) vs Aila (Suikoden III): Stocke has a 2HKO... but Clay Guardian should ward that off. Aila has a 5HKO with physicals which inflict freeze... but Stocke can block that. (She also has a 3HKO with a super-slow Earthquake, who cares.) It depends what stats he has to give up for this, I think, since otherwise Stocke can run her out of resources until he gets a limit or whatever. There's Battle Oath, too, so I guess Aila can actually get her physical to outpower Stocke's healing... mm. Actually I think that does it. I don't believe S3 berserk wore off. She still needs to heal turn 3 and every 2 thereafter to not die... Clay, Oath, heal, Oath, heal, attack, heal, attack... yeah that puts her in a position to lock Stocke from there. Stocke could still win by stalling for a limit, potentially... no idea how fast those come. EDIT: I'm down for Push Assault hype, I think, on the other hand. Certainly is another hurdle Aila has to get over, at worst.
Albert Serdio (Legend of Dragoon) vs Ramza Beoulve (Final Fantasy Tactics): Presumably.
Light
Opera Vectra (Star Ocean: The Second Story) vs Tony (Wild ARMs 4): Opera isn't doing better than a 2HKO here. Tony probably 3HKOs her back, 4HKOs at worst, and is 235% average speed.
Umaro (Final Fantasy VI) vs Karn (Breath of Fire): The damage is similar, the durability gap is bigger than the speed gap.
Spar (Breath of Fire II) vs Proud Clod (Final Fantasy VII): I imagine Spar can turtle at higher HP and apply some buffs/debuffs (though slow is out) to tilt things its way. I'm not... 100% sure about this, but I would think so.