KH Sephiroth help

[DarkMaster]

ok, i've been getting my ass handed to me by this bastard. I'm at level 45 and goofy and donald are at 46 and 43 respectively. this guy is friggin insane, his sword reaches across half the god damn area. I've found a way to recover from his instant KO attacks, but this guy is just too fast. 1 minute 38 seconds is my record for staying alive against him. For those who have beaten him, any tips? should i just go raise my levels some more? thanks in advance

EDIT: warning, this thread contains major spoilers, do not read if you havent beat Kingdom Hearts.