There is a recent issue in many countries especially France, saying that animes poison the minds of youths with realistic visual violence. So what! Blame the violence on gangster movies, child abuse, or CNN for showing acts of extremism in the Middle East!
Anyway, the most violent ones I've seen are Blood+ and Ghost in the Shell.
Both have very gory scenes of people being chopped up or shot through the head Lots of hacking and slashing in Blood+ and loads of violent action scenes in Ghost in the Shell.Both of these are masterpieces in the world of anime.