Ch.11...Duel on the rainy bridge right? That was a pain.
I beat him with an smg/grenade combo. You can't hit him when he's looking at you, so basically you're going to wanna use maybe 4-5 hero actions to run past him, and rack up consecutive scratch damage. Then, when he's fully scratched, you use one last hero action to finish him off with a grenade.
That fight is all about timing, and you really can't afford to waste even 1 bezel, so don't miss.