If you found yourself in an abusive relationship, clearly there is a problem and you need help. Call domestic violence hotline and talk to them, that's the first step.
It's hard to give advice whether the person should immediately get out or stay and try to make it work.
Some people may say, "Get out now" but without preparation, this could only aggravate the situation and put a woman's life under threat. There were cases where women left abusive partners and were killed because there wasn't a system in place to prevent further abuse.
So, I once again want to repeat:
"Get help from groups that understand what abuse is and how to sort it out correctly."
In some cases, women have children, and this has to be taken into account, too.
Abusive males may be actually able to change. There were a few high-profile cases where men admitted being wrong, took courses that assist male abusers in changing their patterns of behaviour, and successfully reformed, with the help of their female partners.
Even an emergency escape needs planning. You may not be able to think about everything but women protection groups have seen it all. They will be able to give you tips what needs to be done.
Each person's situation is unique. Take steps to protect yourself and put your mind on finding the right solution. Even if you are simply dating the abuser, it may be worth to talk to a specialist to ensure the decision to break up won't hurt you or your loved ones.