This is not so much as an anti-hero but rather definitely a corrupted, one-way-to-hell, twisted hero. Definitely one of the rarest gory manga where I actually want to read until the end, just to see the hero getting all his "revenge" until the end. Also I want to see what will happen when all his revenge targets died? Will he turn into an elusive devil traveling around the world whispering sweet sweet ideas into the minds of people similar to his situation? So that everyone will bask in the pleasure of exacting revenge as much as he is? Wooosh, would love to see that lol.
The Hero Who Seeks Revenge Shall Exterminate With Darkness