A couple weeks ago this kid that sometimes hangs out with me and my friends started talking to my sister. I've never liked this kid, he's always been two-faced and a big time player, he uses his "friends" to get invited to parties then disses then and pushes them aside when convenient and he treats girls like shit, he fucks them then moves on. He has been accused of raping a girl before, though I actually do trust him that that never happened. He knowingly had sex with his friends girlfriend. He is also 18 years old, my sister just turned 14. When they first started talking it was pretty much just a big joke but I told her then that she was not to get into a serious relationship with him. Then at a party last week he told me he was going to "bring my sister, get her drunk, and fuck her". I told him then that I would beat his ass if he did anything with my sister. Since then they are now dating and he keeps joking about it, knowing that it pisses me off. He has been screwing with me now for over a week and I have continually ignored it, trying to be the bigger person and leave him alone. Tonight at the soccer game I snapped and punched him in the face after he started screwing with me again. My sister is pissed saying I had no reason to do that and that I was just being a dick. Am I wrong in wanting to beat the shit out of him? What should I do about it?