Godlike
Belial (Wild ARMs 4) vs Ryu (Breath of Fire III)
Ghaleon (Lunar: Silver Star) vs Jenna Angel (Shin Megami Tensei: Digital Devil Saga): All four of these duellers are good, but in each case one spoils the other really badly. Next round too.
Heavy
Sharon (Legaia 2: Duel Saga) vs Keith Valentine (Shadow Hearts): Yeah no, Keith with ID blocked isn't Heavy.
Asellus (SaGa Frontier) vs Bishop Stone (Xenogears): Stone's PDef is factored into the damage he faces, so Asellus only 3HKOs him, and he can actually 3HKO first factoring in the death counter. And that's before considering Slow. Asellus pretty much needs you to allow healing (either via the ShadeRobe or via mystic absorbs) to win this, and I don't think I do. (Or not consider boss death counters.)
Middle
Yulie Ahtreide (Wild ARMs 4) vs Melbu Frahma (Legend of Dragoon): Not certain. Maybe later. Kneejerk is Melbu, two blockers make Yulie stats trash as mentioned.
Samurai (Final Fantasy Tactics) vs Warlock (Suikoden IV): Shell just barely lets Samurai survive... but there's a second Earthquake coming. Bizen Boat isn't going to get this done (Warlock has four EQs), Samurai isn't fast enough to 3-2.
Light
Tia (Lufia 2: Rise of the Sinistrals) vs Cray (Breath of Fire IV): Tia 5HKOs (Spark is halved, she still uses it because triggering a counter would be disastrous), and Cray wins in 3 (buff twice then OHKO). However, she certainly has at least a 5-3 to me. Cray can use Speed, but Tia still manages a 5-4. Alternatively, Cray just goes for damage, but he only 2HKOs (with 4% crit), so Tia can just heal until a double or IP. Cray could win with less respect for TB turn spread certainly.