If you PM me, I could give more setups, and even strategies for battle, but the main thing is, make sure 2 of your character's are dead. I'd call that common knowledge, though...
Here's 1 good setup:

Cloud-

Enhance Sword
Mystile
Ribbon

[In Weapon] Hades = Sneak Attack;
Master Summon = MP Absorb;
Knights of the Round = HP Absorb;
Final Attack = Revive;
[In Armor] Knights of the Round = Quadra Magic;
Enemy Skill = Magic Plus;
Speed Plus = W - Summon
Other party members dead from start of the battle, so Ruby puts his claws in the ground.