I gotta go with Darseid on this one. Supreme Kai or Grand Kai would've been better.
King Kai knows Kaioken (can temporarily double his power), spirit bomb (can call forth the power of every being on the planet he's on [presuming he's at least close to goku's skill in that]) and instant transmission (therefore could evade dangerous attacks and is immune to bfr [thus the omega ray]) and lives more easily on a 10x gravity planet then most did on a x1 gravity planet. however He also said the likes of Nappa were more powerful than he and that is nothing small but Nappa isn' exactlyt up there in terms of dbz level power. Unless he could harness a great level spirit bomb (and even them perhaps not) I don't think he can win.