gosh, I hate to think about his personal relationships.

Again, we are not in a position to diagnose - even given more information. A personality disorder is possible but there can be so much more. I could be that it isn't even a mental health issue at all but instead an anger management problem. I would suggest this has likely been a learned behavior as opposed to mental health.

Hard to manage or deal with I imagine. What about forming an intervention.

You may have to make a tough decision and find yourself telling this individual that while they are important to you, you simply cannot put yourself in the middle of this.