The first battle against Magus, easily. Other honorable mentions go to Azala and Black Tyrano, Yakra XIII and the Trial of the Century (not the battle itself, but the scenes surrounding it), the final encounter with Queen Zeal (especially if you have Magus in your party), and the battles inside Lavos' shell.

Quote Originally Posted by Gamblet View Post
By the way, for me, the Giga Gaia fight is almost impossible without Falcon Hit...
Gold Stud and spam Luminaire?