Marluxia from Kingdom Hearts: Chain of Memories.
He is quoted by every guide I have read and every person I have ever talked to, as being "the easiest boss in the game".
HOW!?!?!
I could never defeat him, I still haven't. I played the game for about a month and a week of that was spent trying to beat him. Because this was before Kingdom Hearts 2 came out I actually had to watch the final movie on Youtube because I COULDN'T GET TO IT MYSELF!
I consider myself to be, maybe, an above average gamer and I never really tend to get stuck on last bosses or anywhere in a game for that matter. If I do I can still manage if I check a guide or whatever but I STILL COULDN'T BEAT MARLUXIA! I don't know what it is, but something was wrong with my strategy or my deck or something, but it was really depressing to see all these comments of 'I did it in one go' or 'Hey, the final boss was sooooo easy wasn't he?'