Judgment and unforgiveness are different.
Unforgiveness is a private cell of torture, reserved just for one. The person you resent is not in that cell with you. He is free. Forgiveness is an act of our will, and when we do that, it closes an open door for demonic torment.
Judgment, however, is a cell reserved for two. Judgment by the power of your words condemns and imprisons you both. Luke 6:37 and Roman 2:1 say that we are opening the door for torment in our own lives when we judge someone.
You can forgive someone and still hold a judgment against them in your heart.