The definition of anti-hero is hard to make, the most basic of the anti hero is that in his environment, he is not liked, regardless what he does. But this is not the only requirement, or spidey would be one of them.
Spawn is an anti hero, but even when he was a hitman, he had a lot of humanity in him and wasn't exactly a prick.
I heard of people labeling Wolverine as an anti-hero, but he is a mere prick. And I don't think Alex Mercer is a prick, IMO, he was a complete prick before the events of Prototype, and he deserved what he got, but after that, he wanted to find answers, and you see him having interaction with other characters normally. The only time Alex could be a prick is when you use him to cause chaos in the city, but that's up to the player.
Never read Catwoman, is she a prick? Does anyone know? Just asking.