Hee!
I was playing online scrabble, minding my own business and on a winning streak when I deduced that my opponent was an ex-boss of mine who treated me very badly. (his nickname, the time zone and their competitive assholishness gave it away)
I asked some innocuous questions to confirm and, secure in my own cowardly anonymity, proceeded to mess with his head.
Hee!
How’d you do that?
Out with it then! What are the juicy details?
Nothing too bad!
I considered a death threat: “I know you live at 123 This Street, and I’m coming to get you!” but decided that was too obvious. So I just told him various facts about himself and when it became obvious that I really knew him IRL, refused to disclose who I was. I also told him he was a control-freak jerk. I hate confrontation of any sort, so even when I walked out on his stupid job I didn’t ever have it out with him, so it was a catharsis of the wimpy kind to tell him what I thought of him.