I discount DLC because its not an option to everyone in the game, besides, Auto Life+Auto Phoenix would defeat her would defeat her, not to mention Wakka can do 1.2m HP damage and Anima can do 1.6m with their respective limit breaks.

When it comes down to it, the Auto abilities will over power any other final fantasy game.

Weapon:
Evade and Counter
Break Damage Limit
First Strike
Triple Overdrive

Armor:
Ribbon
Break HP
Auto Phoenix
HP+ 30%

Rikku: Hyper Mighty G (Shell, protect, haste, regen and auto-life on all characters)
Tidus: Blitz Ace
Wakka: Attack Slots

Every other final fantasy playable character: Dead.