Backfire

Backfire

Meaning:

to produce an unexpected / undesired / opposite result.

If your plan or action backfires, you get the opposite result to the one you wanted.

Example:

The new stricter school policy may backfire and do more harm to the students than good.

Her plan to lose weight backfired. After losing 10 pounds, she started to eat a lot again and gained 20 pounds quickly.