Part 1 of a very tough battle here. Ultima Weapon's Light Pillar kills any character instantly, and he has other nasties as well, such as Meteor and Gravija. Use Meltdown, and Cerberus, then cast Aura on your characters, and let fly with their limit breaks, and if possible, use Bahamut, and magic such as Meteor. And the one thing that you really must do in this battle, is to draw the GF Eden from him, it's well worth it, you really don't want to miss out on the strongest GF in the entire game!