MY EVIL CLOWN FRIEND

When it comes to Batman villains, you're hard pressed to find one half as terrifying as the Joker.

The Joker spends his days forcing people to smile. He's obsessed with seeing those teeth, beaming back at him. He pumps people full of weird chemicals to create these bright, shiny smiles. Or, he'll spray people with laughing gas to keep them incapacitated.

The reason that the Joker is such a frightening foe - the bright smiles, the weird chemicals, the laughing gas, the inappropriate suit - he plays on mankind's genetic fear of dentists.