Suggested by Sonic Lightning is one of the strongest Final Fantasy protagonists, probably only Cloud can really match her. While Ash sometimes coasts by because of his massive advantage in numbers, that won’t work quite as well against Lightning and her Odin. Odin would do a good job of handling many of Ash’s Pokémon while Lightning goes after the heavy hitters. I don’t think Ash is quite prepared to defeat an enemy like this. Lightning wins.