How do you defeat Ansum in Kingdom Hearts 2?

Answer 1

Specify who "Ansum" (really spelled "Ansem" is) in KH2. There's DiZ, who's really Ansem the Wise; Ansem, the Heartless of Xenhanort; and Xemnas, the Nobody of Xehanort and leader of the Organization. If you meant DiZ, you don't fight him in KH2. If you meant Ansem the Heartless, you destroyed him in KH1 at the very end. If you meant Xemnas, then I can tell you that you must fight him many times with different strategies and scenarios at the end of KH2. He's very tough to beat, so if I were you I'd be prepared. I can't tell you exactly how to do it, but you've got to equip yourself with powerful abilities and items so you won't use up all your MP trying to heal yourself in the beginning.