Carrying the negative feelings of hatred, anguish, jealousy, dissent etc. for someone caused you some harm, is like carrying a load of rocks on your head kept by another.
That someone is gone, even moved on May be, may not even remember what they did to you. And here you, eve after years are still carrying that load of rocks they left on you.
They won't return, they may or not apologize. Irrespective, the only person who can free your head from that weight and your soul from the suffering is YOU.
Put that load down, let it go. Forgive... not because they deserve forgiveness, but because you deserve peace.
Remember forgiveness doesn't approve the behavior. It only means you care more for your peace than the anguish caused by another.