NGU Idle is a relatively entertaining idle game. Its developer also explicitly trolls players in-game. There is a “troll challenge” where random annoying things happen, from losing progress to spamming pop-ups to a slowly moving picture of a cat. But for my money, the best one is having a “did not drop” message for a particular rare drop item. It says that you see the ring, but it crumbles to dust before you can pick it up. Better luck next time!
I am imagining WoW raids, where a boss’s death animation includes visibly dropping a legendary item for your class … which an NPC zips in and swipes before you can do anything. That would be the most hated NPC in the game, and players would buy an expansion solely for the chance to kill it.