Lex captures Clark and with spaceship shenanigans, impregnates Clark with a child containing both their DNA. No sex, just a spiffed up turkey baster strong enough to perforate a Kryptonian's midsection.
Cue months (more than 9? Less? Up to the author) of Clark being subdued in such a way so that he doesn't escape and can't harm himself, body horror, and Lex being creepily gentle with Clark until he's rescued by character of author's choice.
Optional Bonuses:
Clark doesn't know why Lex has him captured/he's pregnant until much later.
Lex punishes anyone who harms or even attempts to harm Clark with extreme prejudice.
Lex murmurs thing to Clark midsection, whether he's showing or not.
Clark is rescued before baby can be extracted, so they have to take Lex/head scientist along with them.
Clark&Lex noncon mpreg
Cue months (more than 9? Less? Up to the author) of Clark being subdued in such a way so that he doesn't escape and can't harm himself, body horror, and Lex being creepily gentle with Clark until he's rescued by character of author's choice.
Optional Bonuses:
Clark doesn't know why Lex has him captured/he's pregnant until much later.
Lex punishes anyone who harms or even attempts to harm Clark with extreme prejudice.
Lex murmurs thing to Clark midsection, whether he's showing or not.
Clark is rescued before baby can be extracted, so they have to take Lex/head scientist along with them.