I don't think it really counts since that's a story battle. Then when you fight him the next few times he becomes laughable. Actually, the boss that made me go OHSHI- even more was Id, especially after I realised that he was dodging freakin' everything.
Id was fortunately somewhat slower than some other bosses. Speed is the true power in the game. Usually.
Disk 2.
. Oh and
. Damn both of them. The latter was easier though. And even though the former is optional to complete (i.e. a story battle), it still is possible... yet I've never been able to do it.
Also Redrum, Bloody(?), etc.
Those abominations used to give me nightmares.