backfire
To have a plan go wrong and make things worse.
When something backfires, it produces the opposite result from what was intended, often making a situation worse instead of better.
Imagine spreading a rumor about someone to make yourself look good, but everyone finds out you started it and now nobody trusts you. Your plan backfired. Or picture a student who tries to get out of homework by claiming their dog ate it, but the teacher calls their parents and they end up with extra work. That excuse backfired spectacularly.
Backfiring often happens when someone tries to be too clever or cuts corners. A coach who yells constantly at players hoping to motivate them might find the strategy backfires when the team loses confidence instead. A brother who hides his sister's book as a prank might have it backfire when he gets in trouble and loses his video game privileges.
The word captures that ironic twist when your actions create exactly what you were trying to avoid. When something backfires, you don't just fail. You make things worse, often in ways you never imagined.