In Karathnai (Salthan) there are no explicit words perse, and there is no equivlent to the F word. (though honestly I'm not sure that makes much sense, and maybe someone would invent a course word for sex.).
Note: | is a click.

thed - crap!
|aka - Idiot!/Liar!)
usergs |akausher - Go to hell ("the unknowing low place")
usergs (tosa) - Damn (you) (literally "go down", though there's no sexual connotations to this.)

More Strong/Explicit
dokshidas - Prostitute/Whore/One who visits a Whore
dokeshidasusapa - Son of a prostitute/One who visits a whore
kalnesekas thed - dung eater
ynulusapa/ynulusapi - bastard (lit. "son of the saddle") / (female version)
kesi - Female Kes (a large reptilian beast. Akin to "bitch" in our world)
kesiusapa - Son of a Kes
skene - Human word for "Skin" with inanimate object affix. Slur against humans.
ulasoliusher - butt-lickers (slur against Sulvanians, who are cat-people)