What's the meanest thing you ever did as a teen?

I once read that girls are at their most evil at 14 years old. I feel like we could all agree with that — I'm STILL coping with the psychological torture of middle school.

But now's not the time to air our grievances. It's the time to take accountability. What was the most evil thing you ever did as a teenager? And what was the fallout, if there was any?