That person sounds pathological if not psychopathic. Seems like he needs help. Certainly, there is no way he could have NOT been harmful for the community. After we establish that fact, it's unclear what action would cause the highest 'net' gain of positivity in the community. Should he receive medical attention, psychological attention, medication, punishment?
What do you think would be best?
He had psychological help, but the aid of psychological help where I'm from is generally focused on locking you up and away and pumping drugs into you until you act like what they consider healthy. He didn't do well there, and when it came down to his friends helping him he wasn't doing to great obviously because every time he had alcohol which was frequently he would lose his cool. Yes, he was a pathological liar with sociopathic tendencies. I think the best medicine for him might be to have his ass kicked when he's acting like that and bring him down a couple pegs to be totally honest. I think that would have been a better medicine than any medication. His mom let him get away with too much, and he became spoiled and acted as though he was the most important god-like person on the earth, and likely still does.