Snape/Lucius is not just usually dark, there's about zero possibility of a hopeful ending. Some fairly dark fic can have that, but Snape/Lucius? It's just not my cuppa, no matter how gorgeous the writing or how hot the men.

Same with Remus/Sirius. I've read a few fun MWPP-era fics, even though I'm not that interested in their school days, but I *really* don't want to read post-Azkaban R/S. It's a guaranteed unhappy ending. :)