I'm looking for a manga where main character is "falling to the dark side" because of what happened to him. Something along the story of Kilico:
Spoiler (highlight to view)
The main char from cop becomes a hitman for mafia just to get his revenge
Can be also manga where antagonist is presented well enough so you can understand his motives and why did he go to the evil side.
And yeah I did read Berserk.