The first thing which you should do is to take the women to the nearest medical facility and get her treated for whatever wounds she has sustained. The process of healing the internal and more painful wounds will follow.
If you are a relative to the battered wife, try to tell her that all men are not same, and assure her that good things will come in near future. Give her your shoulder to cry and assure her that you will help her in getting out of the life she has been dealing with.
File a police case on the behalf of the wife. Don’t let the husband escape scot-free. He has committed a crime and should pay for that.
Consult a NGO for women rights and register a case with them. Find how to file a case against her husband if she wants a divorce. Tell her that you are going to help her until she gets a separation.
Talk to her about what had happened in the past and allow her to let the feelings out. Be patient though as there are high chances of an emotional breakdown and what follows is a barrage of tears which you have to sustain.