misery-top
when you tell someone something slightly sad and they respond in saying something much worse, as though trying to win a competition that only they are participating in.
Person 1: "I had so much homework this weekend!"
Person 2: "Well I got attacked by a bear!"
Person 1: "Way to just misery-top me."
Person 2: "Well I got attacked by a bear!"
Person 1: "Way to just misery-top me."