I assume that reasoning with him is not an option, as I've seen the occasional family member or friend go through similar circumstances. I myself have been known to get belligerent with little or no provocation a time or two in my life. If you can ever get them to hear how they sound, it might help. Sometimes somebody would say i sounded just like my Dad, and that would make me think because my Dad had this great big booming outdoor voice, because he worked outside all day. Well that was fine for the back forty, not so much fun at the dinner table "PASS THE ROLLS PLEASE" (geez dad, could you turn down the volume?).

Another tactic might be to get one of his outbursts on video and ask him to watch it. That can be a real eye opening experience, as he may not fully understand how far this has progressed.

Another idea would be to refuse to deal with him until he gets help. Tel him "I love you, but I am not going to talk to you until you get help with this problem. I miss the old you, and when he comes back, I'll come back and talk to him."

Some folks have had success by just leaving the room (or house) every time the offender gets loud, and coming back another day. Don't say anything, just leave, or maybe you could say, "OK, I'm leaving now."

Perhaps the personality changes which are causing him to be very annoyed and argumentative quickly is psychical or a mental health issue. In either case, the person needs to be stopped, before the violence escalates.

My ex husband had some personality changes that caused him to be argumentative quickly; it was shortly before he was diagnosed as being bipolar. I have a teenage son doing similar things, but on a much smaller scale but I think it is just pressures of being a teenage and heading into adulthood.

I would suggest that you tell him, he needs help to control those issues and until he gets the help that, you are off limits for anything. Stick to your guns, and this person will seek the help if he wants you in his life.

Help can come in the form of mental health counseling, anger management or counseling that finds the route of the problem.