I'd like to rec a Clex slavefic, Destiny In The Blood, by me_ya_ri. It re-works some Smallville episodes, but the AU twist is that Krypton was a matriarchy, and all the males were biological submissives. There were exceptions, General Zod being one of them (I guess "Kneel before Zod!" has a whole new connotation, eh?) ;). Unlike humans who enter into Dom/sub lifestyles due to psychologial need, Clark must seek out a Master because it is a biological imperative! He chooses Lex, who is early seasons Lex (whom we Clexers fell in love with), not later seasons, and the story itself is full of sex, kinkiness, plot, action, and love. Kara is wonderfully written in this story (she appears several chapters later but is very important).
Now, Clark is very submissive in this story, but his essential personality is there (as is everyone's but within the context of D/s), and I had no problem with it because I believe he's a natural sub, anyway. :) But he is biologically-driven to submit, and he's very lucky to have found Lex!
So, if you like slavefic or are curious, I'd suggest checking this story out! It was written for NaNoWriMo, so it's 30 juicy chapters of Clexian goodness! She's got clear warnings about what's in her story, so if it's not your cup of tea, don't read it! But it's really well-done. :)