Emotional wounds cannot heal without an apology from the person who hurt you. If the person who hurt you does not ever acknowledge that, the emotional wound is left unresolved and it can really leave lasting aftereffects on your perception of the world and how you act towards other human beings.
When the person who has wronged you feels absolutely no remorse for what they did to you, feels that they were 100% in the right, and will under no circumstances will ever take responsibility for their action, what should you do? I feel like trying to repress or forget about it is not a good way to deal with it. I feel like the conventional wisdom of "don't be bitter; hanging onto hatred for a past wrong only poisons your emotional health; learn to forgive people, not for their sake but for yours" is sort of a cop-out because the person who wronged you will feel completely free to do that sort of thing again in the future to other people because they will never face consequences for their actions. If someone were to steal from you, or sexually assault you, or cheat on you, or any possible thing that would hurt you physically or emotionally, there's nothing you can do to bring emotional resolution? Trying to get an apology out of them would only result in them either deflecting blame or giving an insincere apology to try to get out of trouble. Do you just have to accept that this person will never issue you an apology or acknowledge that they hurt you? You just have to eat the cost of a deep emotional/psychological scar?
Main question/goal: What can you do to let go mentally and emotionally of someone's wrongdoing against you? So that it is not something that you are still bothered by, not something that you give too much thought to. With the main constraint being that they will never apologize.