I hate the Affair Partner, can't stop thinking about it

277 days since d-day, I am 27yo male. WS is 28yo female. She fucked a guy that works for her over 20 times in one week. I hate him, I have revenge and torture fantasies running through my head all day... gruesome shit thay I'm pretty sure would violate community standards if I posted... I've never hated anyone as much as I hate him. This weekend went to a wedding and was fuming the whole time... I found myself loathing the happiness of the married couple, resenting that I am left out here as a shell of a human being while this fuck is out there living his life... Seeking revenge would ruin my life, he isn't worth it, but everything else is just so fucking unsatisfying. Dammed if I do dammed if I don't, if I do something to him I fuck up my life and make myself look like an idiot, if I do nothing I obsess over all the things I WISH I could do to him. I read somewhere that men generally focus more on the AP and women on the WS... This guy was INSIDE MY WIFE and the mental images don't stop. Fuck cheaters.

Edit: We are divorced. The AP was a mutual friend that I trusted and was aware we were married at the time of the affair. No kids. Already tested for STDs and clean. WS displayed no remorse and blamed me for cheating. I am seeing a therapist. There has been no contact with ex or AP since the divorce. I am not looking for people to tell me how I should feel, who I should be angry/not angry with, or how I should be responding in general. I am here for support NOT advice. To clarify I am not NORMALLY this angry but I think being at a wedding triggered it.

Update: Had a session with my therapist today, super helpful. He walked me through why vengeance is a self-destructive path. I told him about how emasculating it was to do nothing, he compared me to batman. He said one of the reasons batman is a hero is because of what he DOESN'T do, how he chooses NOT to kill. He said me choosing to do nothing was a sign of strength not weakness, it was a very empowering thing. He said I was able to redirect me feeling bad because of the AP, to me respecting myself while feeling bad FOR the AP. Feeling bad for what he is, what he represents, the depths he's steeped to. Thank you friends for being a listening ear.