* The Conqueror Worm is a gigantic caterpillar-like EldritchAbomination that does nothing except eat, and grow, and eat, and grow some more. If Hellboy and Roger hadn't stopped it, it would have continued doing this until [[ApocalypseHow it has eaten everything on the planet]].
* The Crooked Man's face is extremely [[http://4.bp.blogspot.com/_edfdVc9_vCE/S1R3Eh7Dg8I/AAAAAAAAAog/Ps_JYdvCil8/s400/Hellboy-The+Crooked+Man2.jpg unsettling]].
** From the same story, we get a witch that can take off her skin and turn into a raccoon, the deformed descendants of the colonists who disappeared from Roanoke and the general creepiness of the setting in the Appalachian Mountains.

* Kroenen when he's shown without his gasmask and almost completely naked. He's covered with [[CoveredInScars huge, grotesque scars]] from his surgical addiction. His eyelids and upper and lower lips have been completely removed making him look like something that crawled out of the UncannyValley. And it was all self-inflicted.
* The Tooth Fairies. They sound cute, until you consider the fact that getting caught in a swarm of them means that you are EatenAlive.