Sephiroth. I was at level 42 and didn't have accessories on to protect me from all the devistating status-defects he does to you. Barret was the only one with protection and all he had was against Frog and Mini. So he still go confused and poisioned. The battle raged on until Sephiroth ran out of MP. Then I just wasted him. He doesn't have a whole lot of moves that can actually kill you. Just put you near death.