Crossed - Probably pretty well known by now but the western comic book series Crossed by Garth Ennis is rather infamous for it's graphic content ranging from mutilation and cannibalism to sexual violence. Although I've not read any beyond the first volume, I'd heartily recommend it for any who have not yet given in a read!

The story follows the outbreak of a virus that leaves the infected with a cross-shaped rash/scar across their faces and lowers any and all inhibitions and raises tendencies for extreme violent or self destructive behavior. It reads a bit like a zombie/post-apoc setting with survivors on the run from various roaming packs of the crossed with much of the tension stemming from the fear of just what nature of unspeakable things they might due to any non-infected who fall into their hands, and always there is the ever present fear of the protagonists becoming infected themselves... and what they might then due to their comrades or loved ones.

The series is easy enough to find in local comic book stores and online.