also if its unclear i do think a lot of lucifer and sam is likened to that of domestic abuse. i kind of run with that in my portrayal. it is a one sided thing completely--sam feels absolutely no positive attachment to lucifer, lucifer does not make him feel safe, or loved, or protected, etc. he doesnt cling to lucifer the way a domestically abused partner might because they love their partner; sam doesn't love lucifer.
but lucifer, imo, loves sam. not in a good, normal, healthy way, but in a possessive, obsessive, ownership way. in a narcissistic way. sam is his property, sam is an extension of himself, and that is the only way he can love sam. he hates all other humans and of course demons. he only genuinely loves other angels (and even then.. he's clearly okay with killing them, if not happy to.)
he sees sam as his. as a thing that he owns and cherishes, as a precious object. he does not see sam as an individual.
this is what creates the kind of boiling rage he'd have to experience to rape sam imo. like, michael hurt sam in the cage plenty, but it was all.. beatdowns, angelic abilities, atomizing, etc. like corporal punishment but worse. i just cannot see michael raping sam. the sense of power there isn't something he wants or needs, he is already superior, he's furious about being in the cage but some part of him has to know that its partly his fault he's here; he grabbed onto sam himself, if he didnt he wouldve stayed topside.
but lucifer has a "personal connection". sam is his dog and he bit him. that cant go unpunished. i have to imagine being put back in his prison is an enormous mental destabilizer to begin with, but knowing it was your vessel that did this to you, the thing you think is beneath you by all means and simply an object, an item, it totally makes sense to me that lucifer would find any means he can to hurt sam.
because he loves him in his own perverted way, and because he hates him. because if he cannot have him, he will ruin him so no one else can.