Drace

1) First off, make sure you have gaurd and counterattack on and dodge roll off. You should also have aero and cure set as your shortcut spells. Equip elixirs in your item slots. When Riku lunges to attack you, press square to block him and then hit him with as many combos as you can. Use aero, cure, and the elixirs as needed. Rinse, lather, and repeat.

2) The last boss is Ansem. You end up having to fight him more than once.

3) You don't see Mickey until the very end when you've already defeated Ansem for the last time.