Godlike:
Kefka Palazzo (FF6) vs Zeromus (FF4): Kefka's speed is 72 and that's obscene regardless of what standards you use. Either way...Big Bang + Flare isn't this almighty massive 2HKO. Meanwhile, Kefka's got 2 Havok Wings being tossed in. That's 2.8x PCHP WHEN HITTING THE BACK ROW (double if Front Row), let alone the chance to double up on it if you see him 2HKOing. Keep in mind the fact that if you see one havok wing triggering Flare phase, KEFKA WINS. Flare = 50% Health, so if it triggers Flare phase, a second Havok Wing (which Kefka is getting off unless you see Big Bang OHKOing) will kill by definition.
Also, as a reminder, Havok Wing won't trigger a counter. Zeromus does not counter physical skills like Jump, Build Up, or Throw in game, only Magic. Havok Wing is clearly physical.
Van Grants (TotA) vs Cecilia Lyne Adelhyde (WA1): Buffs, smites, etc.
Chaos (FF1) vs Kurando Inugami (SH2): Thinking he wins this slugfest.
Yunalesca (FFX) vs Jade (BoF1): BoltX, etc.
Heavy:
Eirika (FE8) vs Alfina de Pamela (G3): Don't see taking Killer averages as standard so...
Antenora (WA2) vs Jenova (FF7): Antenora's good stuff is magical...Jenova DEATH is a magic tank.
Decus (SO2) vs Suicune (PKMN): To add what everyone else said, Suicune also has Rain Dance and above average speed, making Decus even more screwed.
Hahn Mahlay (PS4) vs Rose (LoD): Immunes Instant Death, Dragoon Form heals her from any sort of scary thing Hahn can do, and she goes first. Hahn dies when Rose gets her second turn as such.
Middle:
Margulis (XSs) vs Meganium (PKMN): Need to look this up, though, sounds like Margulius has the advantage.
Keneth (S4) vs Valeria (Suikos): Yeah, guess her winning a damage race works for me.
Nelis (S5) vs Aika (SoA): Swimmerlang.
Meredy (ToE) vs Albert Serdio (LoD): Kneejerk.
Light:
Zylo (SF1) vs Gogo (FF6): Zylo really sucks so much that Gogo can beat him, yeah.
Hix (Suikos) vs Kent (FE7): Kent looks like Middle Champ compared to the people in this Quarter!
Jean (BoF2) vs Cius (S5): Death.
Rafa Galthana (FFT) vs Fargo (CC): Think Fargo puts enough pressure on Rafa to eventually take her down.