These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Angel Devil Shipping: What Christopher Carrion and Princess Boa would've been, if she had accepted him. Since Carrion is from the lands of Night, and Boa was from the Day, it also would've brought peace to the warring kingdoms.
Complete Monster: Mater Motley. She (successfully) brings about the end of all that is good by making a pact with beings whose whole purpose is to destroy. She releases untold millions of evil insects, then burns the entire world with a massive deathship. She burned down her own house rendering her son blind and killing all but one of her 20 or so grandchildren. And then proceeds to sew the souls of said grandchildren into her dress, using them as a power source and keeping them from truly dying. It turns out all of these acts were just For the Evulz and she's just that horrific of a person. Her abuse of Christopher Carrion for all his life, such as sewing his lips shut for mentioning the word love, is what turned him into a Woobie, Destroyer of Worlds.
What Do You Mean, It's for Kids?: This series is dark. It's also aimed mostly at a young demographic. To add to the... confusion? Amusement? Disney actually bought up the movie (and a bunch of other!) rights before the first book was even published.