Jesus, he has issues. Yes he is spoiled and probably isnt doing anything to make his life meaningfull.
Saying he is going to kill someone isnt normal. He obviously has anger issues and should seek help.
He says hes had a hard life. I think the payback is because i was mostly depressed as he was growing up. His father spoilt him and gave him what he wanted all the time. There were a lot of family issues as he grew up but i tried my hardest to protect him. Its a difficult one as i would really like to ask him to leave but he has nowhere to go but on the other hand i cant take anymore. i sit in my bedroom while he is downstairs watching tv. He just says he hasnt got a life but i cant give him that. He says hes ready to kill someone and is very angry.
First of all, no son hits and is abusive to his mother. That alone is a sign that there is a problem that you cannot take care of.
He needs to get help or get out of your life. Does he say what he is paying you back for? You do not need to put up with his abuse.