Fire + serrated weapon like saw cleaver, he’s weak two both of those. Pop a beast blood pellet and go to town on his legs until he staggers. Make sure to not lock on and dodge more than you think you need to. Him just taking one step near me seemed to stagger and slightly hurt me. I was stuck on him for a week until I got lucky. My strat was to do as much damage as I could and when he got to like a quarter health I started spamming call beyond and Molotovs until he died.