No, Clark is not invulnerable to magic. Just like Kryptonite, magic is a weaknesss for him as was shown in a few Season 4 episodes and in the episodes featuring Zatanna.
In Diamond and Pearl, the Pokémon League's weaknesses are Fire and Flying-type attacks against Aaron's bug-type Pokémon, for Bertha the weaknesses are water for most of her Pokémon along with Grass, Water for Flint's Fire Pokémon except for Lopunny which is weak to Fighting and Drifblim which is weak to Electric and Ghost and Dark attacks are the weaknesses for Lucian's Psychic Pokémon. The weaknesss for Cynthia's Garchomp is Dragon and Ice attacks, Grass attacks are the best match for Gastrodon, Grass and Electric attacks are the best ones for Milotic, Flying, Bug and Fire attacks are the weaknesses for Roserade and Fire attacks are the weaknesses for Lucario.