Godlike
Ryu (Breath of Fire III) vs Yunalesca (Final Fantasy X): Kaiser is noted as immuning draining as well as status, which saves Ryu here since otherwise Absorb would cut him to pieces. Anyway, 'lesca doesn't exactly deal damage at a high rate when draining is immuned, so Kaiserbreath spam should end her in four shots.
Riou (Suikoden II) vs Sephiran (Fire Emblem: Radiant Dawn): Sephiran is truly a pain to put down if you don't have solidly OHKOing damage. <Riou>
Rupert Dandridge (Wild ARMs XF) vs Zio (Phantasy Star IV: End of the Millennium): Zio is probably a bit over 3PCHP to me, so Rupert needs to do about 900 (in his own terms) damage to win. If he has a 3-2 this is going to be trivial. And... that just means Zio needs to be 89% speed or below. He probably is. If Zio is faster than that, he's in better shape, but it depends a lot on exactly how you see Rupert's HP... I'm not certain myself. There's a sweet spot where Zio can 2HKO with MT -> ST and not die to Maximum Risk in the meantime, but if Rupert's HP is higher (so he needs two shots of ST) or lower (so that even MT does too much damage) then Rupert will win anyway. Overall the average of assumptions favours Rupert, I'm pretty sure... it helps that PS4 bosses are actively bad at evasion so Rupert can reliably land his damage, which is often a problem for him.
Cloud of Darkness (Final Fantasy III) vs Prototype Gear (Wild ARMs 4): PROTOTYPE GEAR has a 4HKO here, which means he just needs to survive one Cloud of Darkness turn since WA4 boss turnsplit is a thing. And... there's a chance he survives two Cloud of Darkness physicals? But probably not physical + Particle Beam, and I doubt using that lowers her speed so much that it's 58% or less, which is what Prototype Gear needs to get a quadraturn.
Heavy
Rosa Farrell (Final Fantasy IV) vs Oerba dia Vanille (Final Fantasy XIII): Blocks Fog, inflicts Berserk.
Red (SaGa Frontier) vs Sharon (Legaia 2: Duel Saga): Red should definitely have ways to 2HKO her without bringing her below half health, and she's not 2HKOing him without a Mystic Art.
Hugo (Suikoden III) vs Justin (Grandia): Evasion means I don't have to worry about gimmicky ID physicals today. For all that I imagine the winner just gets fed to Galcian anyway.
Middle
Cleo (Suikoden) vs Brad Evans (Wild ARMs 2): Probably 2HKOs. Probably 3-2's anyway. Might even avoid a 2HKO.
Vivi Ornitier (Final Fantasy IX) vs Gaff Gafgarion (Final Fantasy Tactics): Gafgarion 3HKOs Vivi while draining, and is faster. Vivi can try to alternate Water on himself and damage but that probably has major problems outpacing Gafgarion's own healing? Yeah surely. Maybe Vivi's better bet is just to cast Doomsday twice and pray he 2HKOs? Or he could alternate healing and ... Slow but the stat topic suggests Slow isn't that great. I'm not really sure where I see Gafgarion's HP, but I'm leaning towards him here, he needs "enemy HP = average PC" to be around 280 at the point he's thought. Depends on support credit of course. I'll think about it.
Dart (Legend of Dragoon) vs
Tharja (Fire Emblem Awakening): I see LoD as immune to melee counters, but Tharja's not melee, even though she benefits from melee for her accuracy, so too bad.
Light - Later
Ragnar Ryan (Dragon Quest IV) vs
Saleh (Fire Emblem: Sacred Stones): Ragnar is... pretty close to killing with one physical + Spiked Armour backlash, but I think he falls just short. And yeah, he's slow enough that I see Saleh doubling.
Elementalist (Wild ARMs XF) vs Marivel Armitage (Wild ARMs 2): Magic Blocker should push down any already shaky Marivel status hype.
Innes (Fire Emblem: Sacred Stones) vs
Mustadio Bunansa (Final Fantasy Tactics): It wouldn't be crazy to say Mustadio doubled (he needs to be seen as +2 AS), and if he does... I think he wins? Innes kinda frail. Innes can equip a Longbow to counter but that's a pretty large damage hit so probably not worth it, and arguably Mustadio can get around that with Arm Aim anyway. Close though. Innes wins easily if Mustadio doesn't double for whatever reason.