Superman's supposed overpoweredness is actually somewhat overstated by a lot of people. It really depends on which version of Superman you're actually looking at, because a good number of versions of Supes is actually fairly toned down. There's plenty of foes that can give Superman a hard time - Doomsday (killed Supes, nuff said), Darkseid (his most recent incarnation took the entire Justice League to send him back), General Zod (another Kryptonian), Black Adam (Shazam/Captain Marvel's archrival and magic-user), Lex Luthor (we all know this guy, tends to actually have the resources to acquire Kryptonite if it's actually available), Bizarro (Superman clone), you name it.
Even lesser villains can actually give the Big S some problems in various ways, not just in a standard fight. Superman isn't just about beating the crap out of people, you know. Mister Mxyzptlk's entire schitck, for example, is being a complete troll towards Supes.