Many people are struggling with forgiving those who are not sorry. It's the hardest thing to do when the offending person shows no remorse for their actions. The thing is, they do not need your forgiveness half as much as you do, for holding a grudge damages you more than it does anyone else.
The way to forgive a person who is not sorry is to think about what they have done to you and analyze it and figure out what good did their actions bring to you, how did it help to shape you into the person you are today.
Once you will see that whatever was done to you only forced you on the right track of your life and brought you a number of benefits, you will see how your anger and resentment against that person slowly disappearing.