I forgot a good/bad friend's name

 He changed it on Facebook to his middle name, and I couldn't remember what I used to call him.

I looked through pictures of him for a comment or caption that would have it, but none of them did.

And I looked at another and another and finally I remembered.

I don't remember if I gave him an alias here. I'm forgetting the aliases anyways - sometimes I have to read them in multiple posts before I remember who they are!

Anyways, he did something very bad at the end of school, and then did something that would otherwise have been fine, but because of the very bad thing, this second thing was basically unconscionable.

I never told him that, because even years later I loved him. I was on acid a year after we graduated and I wanted to call him and tell him that if he really needed me, I would be there. That I would always be there, even though I haven't been, even though I never even told him why we aren't friends anymore.

He likely knows why. When he messages me on Facebook (the last time was May 2020) I respond, like a friend. But if he hadn't done those very bad things we would have seen each other since we graduated. I would have talked about my life and my decisions with him. 

If and when I see him, who will we be to each other? Should I write him a letter, telling him that what he was to me in college was very important, one of the most important, but that what he did at the end is a huge problem?

He hurt my best friend. And then nearly came between me and her. And the fact that I haven't fully cut him off is a testament to what he did for me sophomore year, and how much I appreciated it. But I might as well have. I basically have, without telling him. Does he know what he lost? I know what I lost.