Superman's got a semi-well known weakness against magic. When they're not ignoring it, Supes is supposed to be hurt by magic just as much as any human would be. I'd count bending as magic, so some well timed rocks and fireballs to the face would do some decent damage.
They won't, though. The problem with Supes' "semi-well known weakness against magic" is that a lot of people don't know how it actually works (Kurt Busiek explained it once).
Superman has no
special protection against magic. This means that enchantments and spells meant to produce a certain effect can harm him. Take the example of Mjolnir, Thor's Hammer, and Wonder Woman's sword. Both weapons have been used on Superman, but only one actually managed to make him bleed. Both are magic. The difference is in the specific enchantment.
Wonder Woman's sword is enchanted to be able to
cut anything in existence. It's not this way because it's super sharp, it's that way because its particular magic says so. Thor's Mjolnir, on the other hand, is much more magical - he can use it to channel radiation, call lightning, or just whack things. But it doesn't have any particular enchantment on it that would allow it to hurt Superman - and thus it doesn't hurt him in any particular way. The reason Supes gets hurt when he gets hit by Mjolnir isn't due to Mjolnir being magical, it's due to
Thor being Thor.
If you've ever played DnD, Superman essentially has a tremendous amount of AC (armor) and HP (hit points), but no innate SR (spell resistance).
Things that are bent don't become magical just by being bent. A rock thrown at Superman by an Earthbender would just be a rock - no particular magic in it. Of the Avatars we've been shown, I think that Kyoshi would stand a chance against STAS Superman (or any of the Avatars in the Avatar state), but not because of magic rocks - rather, because she's really strong. Island-splitting strong.