What’s wrong with my friend.

Hello, I have a question about my friend. In the last couple of years he has been drinking every weekend and probably once or twice in the week. I dread seeing him now. Whenever I see him he has this strange trait where he suddenly switches from being nice to really evil like. Almost like the awful stuff he says is coming from a dark place. He also drinks very quickly and easily gets drunk. He never used to be like this and it’s sad. He only does it to me so no one else sees it. I then want to punch him and get blamed for starting it.. (I always resist punching him luckily) I think he has a problem, what does everyone else think?