Relationships – forgiveness and love (may 2019 work)

I am really stuck on this. Divorced 8 years ago. Ex husband was a pathological liar, an addict with many addictions and a thief (of my inheritance). He was a lousy father (basically zero interaction with the 5 kids). After 20 years, I called it quits (to be honest a lot of what I just wrote, I wasn’t fully aware of until after the divorce and had access to many documents that he was hiding from me). I can deal with his behaviour by labeling it mental illness, but I still have anger and hatred at what he did. I don’t really think about it as I have moved on with my life in all ways. However, I have used by ex husband as one of the people to use as my study person. I am stuck on how to deal with him in my thoughts (the actions are totally civil, there is no emotion in the present, as he has zero influence on my life and miniscule on my kids lives). Please advise what I should do.