Smallville fanfic rec
I enjoyed Macellum by Sylvia a lot. It's an AU where Lionel takes in the stranded alien (who isn't named Clark by him, obviously) and the family dynamics and byzantine plots, machinations and power games of the Luthors are very convincing, and true to the characters, even to Clark's, who of course is different yet brings his own style to his "Luthorness" so that you can see the canon Clark shine through.