How do I fully move on from an ex?

Basically what it says on the tin. I'm ready to move away and release attachment to my ex, but sometimes I still get in my head about how this situation affected me and broke my heart and how it could have been different. I struggle a lot with letting go of the past, I can even hold a grudge, if I'm not careful. Once someone crossed a line with me, it is very difficult for me to just give a second chance like that. One has to proof through their actions that they have changed. I can forgive eventually, but only when someone takes genuine accountability and doesn't play games and keep me in limbo. I'm not demanding, I just know what I don't want.

I gave my ex many chances, I feel like and instead of taking the opportunity to grow or just basically have a proper conversation to start somewhere(trying to be better), they kept treating me like I wasn't important or a priority in their life, while feeling hella entitled to me at the same time. How is that fair? Spoiler alert: it isn't.

They played with my emotions cruelly: one day giving me hope that they would give me what I want, only to revert back to their old patterns and for me to realize it was just smooth-talk to keep me stuck.

I think I accept now that this person has a lot of work to do on themselves, before they can have a healthy relationship and I think I would free them just as much by letting them go. I was indecisive here as well. I need to work on myself more too, seeing as I stayed waiting for them for far too long. At this point, I'd rather be single, I'd rather be single than pine for someone who only misuses my love to hurt me.

I want to stop, you know, I want to stop talking about them negatively and forget this stuff, but it is so difficult when someone put you in such deep pain through their actions and behaviour. Can anyone relate? I guess I'm seeking support, wanting to know I'm not alone in this difficult situation.