Christopher Carrion, the big bad guy in the story Abarat, is pretty damn scary for a “kids” book.
From the wiki:
Christopher Carrion has a ghastly appearance, with rotted skin like that
of a corpse (or carrion). His lips have scar marks from when his
Grandmother sewed his lips shut for saying the word “love.” Around his
head is a translucent collar filled with a light blue liquid. From the
back of his skull are tubes that let his nightmares crawl out from his
mind and take on a semi-corporeal form, somewhat like a snake made out
of smoke and lightning. It’s suggested that when they rub against his
skin he can relive the nightmares he had. The fact that he takes joy in
this is a testament to his morbid personality. Carrion is also very
quick to anger. He enjoys manipulating people to bring out their inner
darkness, such as telling a pair of brothers that the other was plotting
against them and then watching as they try to kill one another.