I did that once. In my case all I wanted was to tell him (my step-grandfather) that what he did to me was abuse. He wasn't physically violent with me but there were outbursts of anger, yelling, lectures, and it could sometimes come out of nowhere. And for the longest time I didn't realize that was legitimate abuse. So once I did and started to process and grieve over it, I decided to write him a letter simply stating something like "You may not realize it, but your treatment of me was abuse." It was weird for me. I felt that I should give him an opportunity to acknowledge the wrong if he chose to, just in case he hadn't realized it. I left my feelings out of it. I don't know if I'll ever have THAT talk with him. At this point I don't know if it matters to me anymore. He's since apologized to me (it took a few years... I was lucky and moved away and he didn't really keep in contact) and hinted at wanting a relationship but I don't know when I'll be ready for that. But I also know he was abused as a child and a lot of what he did to me and to my grandmother was just his anger at his father coming out and misdirected at us. He was hurting. Knowing that helped me to forgive him.

Of course, you do what works for you. Just sharing my experience.