Feel like it’s about time for me to answer my own question, so here goes:
Twilight for all the reasons already stated, but let’s not forget, it’s the little touches that make these books so godawful-terrible. Like Meyer writing a main character who’s so clumsy she’s borderline disabled, and none of the other characters suggesting physical therapy.
The Amber Spyglass, even though I loved the first two books of Phillip Pullman’s His Dark Materials Trilogy. The first two books had great main characters, vivid settings, and creepy plotlines. The third is just an overdone atheistic tirade with way too many pages dedicated to this army that’s being put together to kill god. I wasn’t offended by the unrelenting atheism; I just hate heavy-handed messages.
The Scarlet Letter is kind of a classic boring book. Puritans aren’t that interesting. Some of Hawthorne’s other work is a little more interesting, but barely.
The Sword of Truth series by Terry Goodkind turned me off with all its gratuitous sex and violence. After the first book, he would go out of his way to have some pervy villain set up situations like incestuous demon orgies climaxing with someone’s throat being cut and their nipples being used for mind control or some crap. Shock value only works so many times; after a point, it just got ridiculous.
My fifth one is some Dean Koontz book I read. There were two teenage guys, one dorky, one popular. The popular one was a psychopath, so of course he eventually turned against the dorky one, and there was a long, long chase through a train yard.