Cousin Bette/YMMV

Alas, Poor Villain: Valerie's death-bed repentance (coupled with the gruesome nature of her death) lend themselves to sympathy. Bette to a degree.
Alternative Character Interpretation: Is Adeline the image of wifely virtue, or is she is just being weak by allowing Hector to get away with so much?
Les Yay: Bette and Valerie's friendship is often interpreted this way.
Moral Event Horizon: While he was a somewhat sympathetic (and even pleasant) character most of the time, Montes committed the single most heinous act in the book when he deliberately infected Valerie with a tropical virus that would kill her slowly and gruesomely (Revenge and Asshole Victim notwithstanding).
Squick/NauseaFuel: The amount of detail given about the dying Valerie's symptoms is gratuitous and might leave the reader more kindly disposed to her.
The Woobie: Hortense and Adeline chiefly. Wenceslas to an extent.