I forget how I came across this fic, but I'm very glad I did. Set late season 10, AU after The Quest, this is a very dark, very angsty look at the warped relationship that is Sam/Baal.
There is snark, clone!death, bondage and (strictly speaking) non-con sex, though since this is Baal and he's perfectly capable of looking after himself, I suppose consent is given just by his being there.
Under Every Green Tree