Like what?
He never would have said "it's my win." He also never would have turned into a psycho; he was always logical, unemotional, and calculated.
Well yeah, that true.
He trusted too much upon his victory that he didn't consider everything, like the fact that Mikami might use Death Note within those days.
Especially when Light had told Mikami that he was in a position where he couldn't make any moves.
He was being WAY too careless. He should have told Mikami to always keep a page of Death Note wherever he goes to emergency situations.
In a way the ending sucked, because it only relied on Light's mistake. No Near getting solid proof or anything. Just a tiny mistake.
Other than that the ending was good though. It's a bit stupider in anime, though, where Light kills Mikami instead of trying to kill Near. And wtf? He's been shot like 5 times and still he's trying to run away. And heck, he's opening to door for like 10 seconds and the other guys do nothing about it.
Manga's better at everything anyway, though.