I have two. The Ritual and Drowning.
The Ritual is pure smut. 61 chapters and every one contains a graphic, demeaning sex scene. I’m convinced the author was an adult film screenwriter and decided to try their hand at writing a novel. There isn’t a single likable character in this book.
Drowning isn’t a great work of literature. I felt that the characters were very two-dimensional. I hated how naive the author made the protagonist. It made me have a lack of sympathy for her. The ending was series finale of Dexter bad.
The Swarm by Frank Schätzing. It was 400 pages too long, all the characters were disaster movie cardboard cutouts, it felt vaguely ignorantly racist, every single little bit of science/etc was explained at length, and every character made stupid, stupid decisions.
If, in a book about the oceans fighting back and killing humans, you still go on a sea dive in a DIVING SUIT at 70% into the goddamn book for no real reason, YOU DESERVE TO BE HUNTED BY SHARKS.