Shadow self work - including journaling, studying my dreams, contemplation, reading Jung.
Past life regression - it can help reframe things for you, these people may make appearances in them and your subconscious seeing and connecting the dots can trigger healing. It may be where the root of the wound is, though you may have more than one past life to review for complete healing. I did a combo of reading Brian Weiss books then https://www.youtube.com/watch?v=xTnAqDPBsoY
(first time had to play it twice before I experienced anything) and then saw a past life regressionist.
Thinking about forgiving the person and sending an intent this is something I want to do by myself without their participation. Just thinking about my desire to forgive from time to time eventually manifested a positive event and then an emotional release. This is after I did the other options and felt like there was residue.
So, those are just the main things I did and might give you some ideas! Best of luck