Hmm, from what I've seen.. The kids in Lucy's school from Elfen Lied. THEY KILLED HER PUPPY FRIEND I AM STILL SCARRED BAAAW ;3; Now let's debate who has the biggest twat in all of anime. xD
I'm still convinced that Itachi had a reason for what he did and that it just hasn't been revealed yet... I guess that doesn't change the fact that he's quite a twat though.
So many hentais, so little time... Each series has a twat in it. I would argue Naruto is the twat in that particular series. & shikab!tch, but that's just because I hate him... As far as Itachi goes, yeah he's a ****** but twat isn't quite the right description.