I think writing a letter might not be a bad idea but I wouldn’t send it. Restorative justice has a component of all parties getting to a resolution and offending party accepting responsibility. Is he going to accept his faults? And how would you know if you intend to block him? And if his faults are him being unavailable, then he already knows it and writing it to him might not accomplish much. Especially if you two weren’t exclusive.

I also think since this relationship ended a year ago sending a letter now might be a strange move. Instead of accepting responsibility, he’d likely think you aren’t over him, not moving on and possibly want him back.

I think knowing that you aren’t going to date anyone like him is already a good closure.