King Sombra unless Tirek has had a LOT of magic meals! Marcus Brody vs Ryoga Hibiki in a race around the world, with several check-in locations ^_-
Samus, she'd just keep rolling and pew pewing till Godzilla went back to sleep! ^_- Tirek vs Shang Tsung in soul eaters eating contest
Ocelot. Marston is good, but Ocelot can pull of shots that Marston couldn't even imagine. The Hero from Fable vs. The King from Fable 3 in a duel.
Twilight Sparkle, because she could launch a thousand devastating attacks in the time it takes Goku to charge up a single attack. Batman vs. Catwoman in a 200 meter footrace.