Years ago, a lad we were friendly with asked me for my number in the pub. I didn't give it to him but someone else apparently did and he bombarded me with texts asking to take me out.
I was a closeted lesbian at the time so tried to politely tell him thanks, but no thanks. I wasn't in any way rude to him but my rejection must have damaged his fragile ego.
A few weeks later we were at the pub and bumped into him and his pals. He was clearly upset with me and called me a racial slur. Everyone at the pub kicked off on him and there was a huge row about it.
After that night I didn't see him for years until he came into the café I was working at with his girlfriend. I didn't acknowledge I knew him and was nice as pie, took their order and prepared their food as usual. When I put his plate down I looked him in the eye with a wry smile and said, "Hope you enjoy your food!".
I watched him hesitantly start eating and he looked so uncomfortable the whole time he was there, checking every forkful before he put it in his mouth. I didn't do anything to his food but the fact he was clearly worried I had and didn't enjoy it was all the petty revenge I needed.