Penance has 12 million HP and has 255 STR, 255 MAG and 255 AGL, it takes 90 minutes to beat... I say you must prefably have from 45,000 to 99,999 HP, 800-999 MP and 255 core stats, 150+ Magic and Luck for everybody, all celestial weapons, weapons with BDL, Triple Overdrive, One MP Cost (for Quick Hits) and Evade & Counter/Counter, Armors with Break HP Limit, Auto-Haste, Ribbon, Auto-Protect/Auto-Phoenix (Have Rikku use Hyper Mighty Guard), you must have Yojimbo pay 5,000,000 gil to use Zanmato or Wakka use Attack Reels, Tidus use Blitz Ace, Yuna or Rikku cast Auto-Life... you must attack Left Arm before it attacks you, removing positive statuses, and Right Arm before it uses Mega-Gravition that tears off 43.75 HP on you and your allies. 45k-99k HP with Break HP Limit is a must and must-have for fighting Penance.