There is a high chance of you getting the custody back as you said your ex-wife abuses your daughter. If the mother is not mentally stable, the father is the next person to get custody of the child. As per the laws on Indian child custody, both divorced parents have equal rights over the child even after legal separation. One parent winning custody doesn’t mean the other ceases to be the parent and loses all rights over the child. If the mother is unable to care for the kid, the child will be given to the father.