Main characters that are impossible to like (Naruto, Inuyasha, Ichigo), female leads that are irritating idiots (Sakura, Kagome), out of place attempts at humor (Naruto, Inuyasha, Bleach, even Full Metal Alchemist), the fact that most of those attempts at humor are "[character] says something blatantly false to impress girl/heroic character, is proven a liar immediately after ending sentence" or "[character] acts like a total idiot when accused of liking a female character romantically," and so on.
Full Metal Alchemist was alright, I suppose, but I didn't watch it very long and that one guy (Hughes, I think) really got on my nerves. He has "one (UND PRECISELY VON) personality trait (fatherly love/pride towards his daughter), a cliche which is not only incredibly annoying but also a sign of lazy writing. I remember the other characters having more depth, but I haven't seen the show in a while.
Oh, and I hate it when they have the character that seems to be functionally retarded (completely naive, personality of a five year old) and then they turn out to be a borderline genius in every variety of schoolwork. Like Orihime.
EDIT: Before you respond, please be advised that I know good anime exists somewhere, I just don't feel like looking for it. Death Note seemed okay for the short time I watched it (clever plans that are actually clever, Light developing a God complex instead of becoming some overly righteous prick, that first little duel between Light and L early into the series), but I lost interest for some reason. I think it was Oblivion, doesn't matter. Anyway, I don't have a built-in hatred for ALL anime, but the topic was why I hate it. And just be glad I didn't mention Dragonball (Z/GT), because it somehow consists of everything wrong with anime, while remaining totally devoid of redeeming features.