why cant i beat penance?

[ScottNUMBERS]

I can't beat Penance can someone help? These are my stats and equipment:

Auron: str:255 def 255 mag: 255 mg def: 255 agil:255 eva:255 luck:134 acc:255
break damage limit, evade and counter, first strike, triple overdrive
ribbon, break hp limit, hp +30%, auto phoenix
hp: 48000 mp: 999
every a-ability (exept his final overdrive)

Yuna: str:255 def:255 mag:255 mg def:255 agil: 255 eva:255
luck:120 acc: 255
Break Damage Limit, Triple Overdrive, 1 MP Cost, Double AP
Ribbon, Break HP Limit, Auto Phoenix, HP +10%.
hp: 38000 mp: 999 (most a-abilitys)

Tidus: str 254 def:255 mag:255 mg def:255 agil:255
luck:79 acc:255
break damage limit, triple overdrive, (two other things I can't remember at this moment in time but I got the caladbolg)
ribbon, auto haste, hp+30%, break hp limit.
hp: 45000 mp:999 (most A-abilitys)

Why cant I beat him?? any ideas?? (Don't say yojimbo or cheats please)