Braev Lee (Bravely Default) vs Ranger (Final Fantasy Tactics A2)
I'm not 100% sure, but I think Default works even against Qada's Poison Hi-Potion, so Ranger can't just go aggro and 2HKO even if you see Braev's HP as "bad" (read: <3 PCHP or so). That said, I don't think it matters, Ranger is faster and drops the status-ailment resistance reduction Holy Water -> Reverse Remedy to give Braev some nasty status then wins I suspect. (Yes, you can status BD bosses, just their resistance is ludicrously high to have like a 0% chance of this working unless you debuff their resistance... which Ranger can do, and his status attack also is a bunch of status attempts at once, so even a 40% rate afterward is probably fine.)
Heavy
Ayla (Chrono Trigger) vs Nera Briscolleti (Dragon Quest V: Hand of the Heavenly Bride)
Coin flip the match. Nera is faster, but Ayla's speed is ATB speed, so even if Nera outspeeds turn 1, she might not outspeed by turn 2 depending on interps. Anyway Ayla 2HKOs, Nera also 2HKOs, although if you see her as slower she can also roll the dice on Thwack's instant death which is.... probably somewhere from 50% - 70% accuracy depending on the suite of enemies held against, so probably also turn 2. Not sure.
Garai (Chrono Cross) vs Corrin (Fire Emblem Fates)
Hmm. Garai is "fast" and goes first but I think Corrin can set up to survive 2 hits with dragonz. Usual disclaimer I allow Revelation Corrin, so open with Dragonstone+ for the tankiness, Draconic Hex on the counter, and then Omega Yato Corrin slashes away on for 2x times + a counter. 3 sword hits + a DS+ hit + maybe Dragon Fang proc should do the job here.
Middle
Freya Crescent (Final Fantasy IX) vs Yusuke Kitagawa (Persona 5)
Luna is a trap here, I think. Freya might win the slugfest post-Berserk if she always hits, but while I think Auto-Sukukaja is a good bit worse than 50% evade, just 1 evasion might be enough here, especially with the damage boost speeding up the fight. They each 6HKO at base here with basic physicals or something pathetic which is upped to a 4HKO, except Inari will be going first. That said... crappy healing is exactly what Yusuke hates, so Freya just keeping up Reis Wind and carefully poking should be fine as long as she doesn't ram into High Counter constantly, and stops attacking to let regen do its work if Yusuke isn't spending HP on attacks. This stally strategy is hypothetically countered by Red Demon Blade & fishing for Despair, but eh, Med = 20% rate IIRC which is just too crappy. So probably Freya, but can be convinced, since "let's throw lots of evadable / counterable phys attacks at Yusuke's face" is in fact his game.
Bartholomew Fatima (Xenogears) vs Elliot Craig (The Legend of Heroes: Trails of Cold Steel)
Bart fails forever at pressuring through Elliot's regen. As long as Elliot heals before the occasional Bart double-turn he can't really lose.
Bo (Breath of Fire) vs Setsuna (I Am Setsuna)
Setsuna should easily 3HKO here off Luminaire x2 -> Holy Light. Question is if Bo can sneak a double turn in by turn 3 against Setsuna's shoddy speed, since she certainly dies if he gets it. Probably not, but Bo is slightly above average speed? Alternatively, apparently (according to Reiska checking a FAQ) HeroBw is wind/water/holy element on its attacks and BoF1 is "unfriendly" about resistances (i.e. they hit the best resistance, not the worst, hence Meeple's low damage numbers off HeroBw), so it's possible Bo misses the 2HKO here thanks to Setsuna's Light resistance. Checking... huh, yeah it does, so no need to obsess about speed. (205 damage vs. 479 no-crit kill point * .85 due to 15% resistance * 2 = .73 damage to Setsuna's .75 Physical Durability).
Light
Selphie Tilmitt (Final Fantasy VIII) vs Silque (Fire Emblem Echoes: Shadows of Valentia)
I'm not sure Silque would win even if Nosferatu had a 100% hit rate, but yeah, 10 Spd is bad, she's getting doubled and annihilated and isn't doing enough damage to close things out fast even when the draining hits. Invoke is suicide (she doesn't get Genny's horde to maybe body block for her).
Marco (Radiant Historia) vs Shura (Fire Emblem Fates)
Heal lock. Guard Boost isn't enough to break Marco out, just double with Iron Sword until he doesn't heal and finish with Silver Bow. Marco can win off a YOLO Sleep attempt but he only gets one. (Okay, he could also win if Shura is incredibly unlucky on getting criticals and he heals into a Mana Burst / Turn Break first, but nah.)
EDIT: Right, I thought Shura was faster than he was, he doesn't double right away. Hmm.. I think if he opens with Silver Bow, then does 2x Silver Bow hits on turn 2 at a slight damage penalty, that should still 3HKO... but... then Marco arguably starts grabbing HP-boost swords to up his durability even a little, and that would let him get 2 Sleep attempts off at the cost of a weaker full damage combo? I'll switch to abstain for now...