Addressing men one day Rasoolullaah
صلى الله عليه وسلم said:
ولن يضرب خياركم
"The best/noble among you will never hit (their wives)."
If a husband abuses his wife, the Nikaah is still valid, but the woman should not live with such a man. In such a case (of abuse), a woman can go to the reliable `Ulamaa with authority in her area, and those `Ulamaa can make Faskh of (break) the Nikaah.
Before doing that, though, they will first call in both the husband and the wife and speak to them, and find out firsthand what the problem is and if there is any solution(s) other than making Faskh of the Nikaah. This is also done to determine if both sides are telling the truth.