I just beat Sephiroth at level 99 with Ultima. I gained 21 levels in a 2- 3 hours by going to the Pride Lands. I equipped the Gull Wing key blade. Then I lowered my health to when there is a alert sound. I then went up to the Peak and used Magnega 4-5 times (each Magnega gives you about 9000-10000 experience) and then regenirated my MP. I was at level 99. All I need to do max level my form levels: Valor- 5, Wisdom- 5, Master- 6, Final- 2. Oh yeah, when you fight sephiroth, don't put on berserk charge. If you get him down to a one health point, you have to kill him with a finishing combo!