It's not about works vs. grace. It's about someone (alive), genuinely apologizing and changing. Jesus didn't freely offer forgiveness to everyone. Not even when he was on the cross.
When Jesus was on the cross and saying, "Father, forgive them they know not what they do," it's common for people to take that out of context. The Pharisees knew who Jesus was, and they despised him. He is saying that God does not hold you responsible for sinning if you don't understand what you're doing or know that it's wrong, just like a child who has not yet reached the age of reason is not considered responsible for his actions.
I'm sure all of us have at one time or another overlooked an offense and forgiven, because we knew the person who hurt us really didn’t know what he was doing, made a genuine mistake, is not normally malicious, didn't mean any harm, etc., etc.
However, no one who has been in an abusive relationship can say that an abuser doesn't know what he's doing. In fact, he knows EXACTLY what he's doing. Abuse is intentional, deliberate, ongoing, and often planned out in detail and in advance. It is also repetitive in nature, and the abuser keeps doing it because it works for him.