Most Helpful Guy
Firstly, you are right to want to end the relationship. This is an abusive relationship and he obviously has serious emotional issues. Given that he is prone to violence, I urge you to not break up with him in person. Otherwise, you may get a few new bruises or worse. I'd recommend a phone call or a text message, depending on whether you want to put up with his inevitable outburst. Texting is impersonal but he cannot yell at you. If he asks why then you can just tell him that it's because he is abusive.
Most Helpful Girl
First, since you know that he physically abuses you, DO NOT break up with him in person. Text or call him just to be safe. Go to a good friends house or a family members for a while so he has no access to you. Why? Because there is a possibility that he can become so angry and vindictive that he either a) Really hurts you or b) kills you. So yeah, break up with him right away because as long as you're with him, the more you are in danger. I really hope I answered your question (: Good Luck, Sweetheart!!