Pretty much the hardest challenge in this game maybe even the entire series. Sephiroth was not at all designed for no damage. Strike raid has to be used in order to pull it off but it's still very tough. I didn't use strike raid at all in phase 3 though and was super risky and aggressive.
No Damage
No Magic
No Stat Boosts
No Limit in Phase 3
No More Than 1 Item
No Ultima Weapon
Meteor Skip
Under 6 Minutes