Should I Go To This Party (Please, I need advice)?

Ok, So im in need of help here. More along the lines of what you think. So im invited to this party. My girlfriend and her brother are hosting it. Its a summer kick off party with about 30 or so people there. But see there is going ot be this guy there that hates me. He wants to basicly beat my head in with a bat. She use to date him. Hes asked favors (sexualy) from her. She tells me that she did not do anything. But there really good friends. I think to good. but anyways. Im pondering on weather or not to go to her party because hes going to be there. Hes told me before that he wants to beat me up. With the party comming, im almost temping to stay home and not go. This way i dont put myself in that situation, where he can act on me some how. I want to go badly to be with her, and friends, but at same token i dont want anything to happen. Shes already pissed and mad because shes under the impression i cant go. She says that he wont act, hes not that stupid to at her house, or with that many people there. But im thinking other wise. What should i do? im under the impression dont go, as much as i do. By not going i dont leave open that option for him to act. Please Help, Thanks so much. Im really tied here. I told here im not going because of him, and i dont want anything to happen. PLEASE ADVICE, THANK YOU SO MUCH! SORRY IF ITS LONG!