Liar, Liar
There was a kid in my class who would purposefully do things to hurt other kids emotionally. He constantly lied—including to his mother—in front of my face. When he was called out on it, the mom laughed. She always defended his behavior.
In my many years of teaching, he was the only child I had ever remotely come close to hating. And so I got a little petty. After several months of his awfulness, I started waiting for the days when he was absent to do any extra special lessons and activities that were extremely fun, so that he would miss out on them.
Then when he would come in the next day, I would have the kids write in their journals what they learned about, and what they enjoyed about the activity, just so he would know he missed it. Story credit: Reddit / quickwitqueen