Homonym: kryptonite (Weakness)
Kryptonite is a fictional mineral from the DC Comics universe, primarily known as the weakness of Superman. It is often depicted as a glowing green rock that emits radiation harmful to Kryptonians, causing them to weaken, lose their powers, or even become incapacitated.
The concept of kryptonite was introduced in the 1940s and has since evolved to include various forms, such as red, blue, and gold kryptonite, each with different effects. Kryptonite has become a cultural reference for anything that poses a significant vulnerability to a seemingly invincible person or entity.