Violence Jack (the uncut version, which is hard to find, even online) was here. Everything else is small time. I'm not even sure I'm allowed to mention some of the things that happen in those three episodes, which may also be the worst in the history of Japanese animation. If you watch it, I suggest you get some steel wool ready to scrub yourself with afterwards. And when I say worst, I also mean that it fails so completely as a work of film that Manos: Hands of Fate looks competent in comparison.
It is worth remembering that, whatever anyone tells you, the most violent anime was all made during the late eighties and early nineties when the OAV market was in full swing. The gore and insanity in titles like Angel Cop and Apocalypse Zero put modern attempts to shame in terms of detail and animation quality.
As far as manga goes, I think that Violence Hero Riki Oh has a title that speaks for itself. Don't watch the anime, though. It takes out all the good parts.