How do you beat Sephiroth in Kingdom Hearts?

Get to lvl 80, then use all the last chance and any other health and life saving ability. Have thunder and cure on the quicklist. About halfway through the fight he will use an ability where he starts to glow. USE A COMBO at this point in time. he will be hard to reach. When you can one hit him, use thunder.

also remember to equip beserk (not a drive) and watch out for the rocks that he calls.

enjoy!