The way it's going to work for now is: first violent scene, MC beats the bejeebers out of a guy with his bare fists. He's cool, almost regretful about it, just trying to make a point so he can head off future trouble. He isn't aware of how torn up he is about it inside. Second violent scene, MC is in a rage, vengeful, full of hate, enjoying the guy's distress and trying to prolong it. This time it's physically removed, with a gun so there's no sensation or contact involved. This time he steps back mentally from himself at some point and can't recognize himself. Probably that's when he ends the torture and kills the guy.

I'm not sure yet how this all works around to fit in the story arc, but I think whatever he recognizes in that second scene is one of the keys to the book. I think there's maybe one more violent scene where he has to deal with whatever he realized about himself in the torture scene--maybe at that point he sees he has a choice to make about the kind of person he is, and makes it? Dunno. I kind of have some ideas about who's in that last scene--it may be the next to last scene in the entire book--but am not sure yet.