1. plural of kryptonite; a substance (especially in Superman fiction) that weakens or destroys a superhero
Usage: often capitalized when referring to the fictional mineral from Superman comics; commonly used in popular culture and entertainment contexts
2. a person's or thing's critical weakness or vulnerability; something that can undermine or destroy someone or something
Usage: figurative use; informal

Examples

• In the Superman movies, kryptonites are fragments of his destroyed home planet.
• Public speaking is one of his kryptonites; he always gets nervous in front of large audiences.
• The team's kryptonites are poor defense and inconsistent free-throw shooting.
• Social media has become a kryptonite for many politicians during election season.
• Her perfectionism is both a strength and one of her kryptonites.
• The company's kryptonites include outdated technology and slow customer service.
• Different colored kryptonites have different effects on Superman in the comics.