Please help, messed up problem.?

Ok so yes im young and yes this is over a girl but try to view my point...I went out with this girl and we broke up. My "friend" knew that i liked her and still went behind my back and did thing with her(hj,finger,etc..) Me and this kid aren't good freinds at all. We used to be close and now we just don't talk at all. Anyway, I was going out with a girl and we broke up and like a week later he was talking to her and trying to get with her. THey did and i was fine with it because it was the first time. The second time i went away and he told her all lies about me and she dumped me. Then he has done this a few more times with other girls. Now i got close with a girl again and guess what he did...broke us up and did stuff with her. I know this sounds dumb but im soo done with his ****. Hes a little scumbag who thinks hes a pot head and has no freinds at all. I hate him so much and im thinking about killing him. I want to kill him so that i nver have to look,talk or ddeal with him again..I really dont know what to do..PLEASE help me