How do i break up with someone that threatens violence?

Find support: I would recommend that you have a strong support group consisting of either friends, relatives, etc. They need to be with you when and if you do decide to end your relationship. Unfortunately, we can not always control the actions of others. If you were hit or injured you need to obtain a restraining order.

Serious: This can be very serious--"violence" may mean lethal. You should quietly work out a plan of action (this is a common situation and good advice is available) in advance at a domestic violence crisis center. They will have connections to all the resources you may need, depending on the specifics of your situation. Better to over- than under-prepare. Don't try to go it alone.