What I did was Level up to at least 90, and made sure I had plenty of Elixrs in my items slot. To fight him I used trinity limit on him, and by now you should have the Ultima Weapon. Do this, and your sure to beat him, but know this you may not beat him the fist time. I didn't, but I went back and then beat him, and I really am not trying to brag. But I beat him on Proud mode, second try. Which isn't bad because it was my first time playing it on Proud.