First confirmed on Radio, “The Adventures of Superman (June 1943) and in comics, Superman #61 (November 1949) Superman’s weakness is the green kryptonite. Exposure to its radiation nullifies Superman’s powers and weakens him with pain and nausea and will eventually kill him with long exposure.
Even though green kryptonite is the most commonly seen form, over the years writers have introduced other forms: such as red, gold, blue, white, and black, each with its own effect. Gold kryptonite, for instance, permanently nullifies Superman’s powers but otherwise does not harm him. Superman is also vulnerable to magic, this weakness was established in Superman #171 (1964). Enchanted weapons and magical spells affect Superman as easily as they would a normal human.