This is the 10440th most frequent French word.
kryptonite
Kryptonite (French): A fictional substance that weakens Superman, metaphorically used to describe someone's weakness.
Here, 'kryptonite' refers to the physical material possessing weakening properties for Superman.
Superman devient faible lorsqu'il est exposé à la kryptonite.
Superman becomes weak when exposed to kryptonite.
In this case, 'kryptonite' metaphorically represents Marie's challenge or weakness.
Pour Marie, les mathématiques sont sa kryptonite.
For Marie, mathematics are her kryptonite.
Here, 'kryptonite' symbolizes a hindrance or difficulty encountered during performance.