bogeyman.

A menacing, ghost-like monster in children's stories.

Any make-believe threat, especially one used to intimidate or distract, or a real threat greatly exaggerated for those purposes; often taking the form of a notorious historical personage suggested to return as a revenant to punish for wrongdoing.

The bogeyman of a Halloween-candy poisoner behind every door has animated occasional moral panics against trick-or-treating.

The specter of an election-vote recount is this year's political bogeyman.