Another fairly well-known weakness of Superman is that his powers don't work on anything of magical origin.
In the kind of logic that only happens in comics, Superman's powers originate from the natural world and so have no effect on things from the supernatural world.
This means that against an opponent with magic powers, his punches are only as effective as an ordinary steelless man (although in a weird workaround, he can still swing inanimate objects with superhuman strength) and that his face likes being stabbed by a magic sword about as much as yours would. Not only that, but Superman's Kryptonian DNA actually makes him more vulnerable to magic spells than an ordinary human.
It's a weakness that has led to Superman being on the recieving end of beatdowns from villains like the evil sorcerer Satanus and even fellow heroes like Wonder Woman and Shazam (whose main weakness turned out to be Marvel lawyers copyrighting the name Captain Marvel). Even more surprisingly, a recent team-up saw him impaled on the magic sword of none other than He-Man.
Turns out being a Man of Steel is nothing compared to the Power of Grayskull.