What is achilles heel?!

What is achilles heel?

An Achilles’ heel is a fatal weakness in spite of overall strength, actually or potentially leading to downfall. While the mythological origin refers to a physical vulnerability, metaphorical references to other attributes or qualities that can lead to their downfall are common.
The death of Achilles was not mentioned in Homer's Iliad, but appeared in later Greek and Roman poetry and drama concerning events after the Iliad, later in the Trojan War. Here and in the myths surrounding the war, Achilles died from a heel wound as the result of a poisoned arrow fired by Paris.

According to a myth arising later, his mother, Thetis, had dipped the infant Achilles in the river Styx, holding onto him by his heel, and he became invulnerable where the waters touched him -- that is, everywhere but the areas covered by her thumb and forefinger -- implying that only a heel wound could have been his downfall. Another version of Achilles becoming close to immortal involves Thetis' attempt to make him a god. She would rub his whole body with ambrosia and then hold him over a fire every night. One day, Achilles' father, Peleus came in the home and caught Thetis holding Achilles over the fire. Peleus did not know that Thetis was trying to immortalize Achiles. Thetis was scared and fled out of fear. This possibility coincides with the fact that Thetis left Achilles at a very young age.

The use of “Achilles’ heel” as an English expression for “area of weakness, vulnerable spot” dates only to 1855 (Merriam-Webster).

The Achilles’ heel as a singular weakness is a cliché in superhero comics, most famously Superman’s weakness against Kryptonite.