Well, after a couple closure sessions coming up I may be able to forgive No. 3 for doing something in my interests that backfired badly.

But I think the more usual situation is like with CW - I was mad at her for a few things, but mostly telling me she was worried I'd file a complaint against her and as a result was treating me differently from other clients, which I don't call my best interest. I canceled the next session, making the point in a longish letter that when she said that, it was about her, not me. I ended up seeing her in an emergency session two days ago to discuss a divorce development. We talked mostly about that, but at the end she said "we should talk about this in more depth when you get back, but I wanted you to know you were absolutely right in your letter, I made that session and those issues all about me." So I don't know about trust or forgiveness until I see her again, but it's a good first step.

I think to forgive or trust the other party has to display self-awareness and demonstrate contrition. Which do not sound like your ex-therapist's strong points.