Achilles' heel

In Greek mythology, Achilles (also Akhilleus or Achilleus; Ancient Greek: Ἀχιλλεύς) was a Greek hero of the Trojan War, the central character and the greatest warrior of Homer's Iliad, which takes for its theme the Wrath of Achilles.
Achilles also has the attributes of being the most handsome of the heroes assembled against Troy, as well as the quickest.
Achilles's death came as divine retribution for his hubristic murder of Troilus. The Trojan boy had spurned his sexual advances and was killed by the enraged hero inside Apollo's temple.Later legends (beginning with a poem by Statius in the first century AD) state that Achilles was invulnerable on all of his body except for his heel. These legends state that Achilles was killed in battle by an arrow to the heel, and so an "Achilles' heel" or Achilles' tendon has come to mean a person's principal weakness.

According to the incomplete poem Achilleis written by Statius in the first century AD, and to no other sources, when Achilles was born Thetis tried to make him immortal by dipping him in the river Styx. However, she forgot to wet the heel she held him by, leaving him vulnerable at that spot. (See Achilles heel, Achilles' tendon.) In another version of this story, Thetis anointed the boy in ambrosia and put him on top of a fire to burn away the mortal parts of his body. She was interrupted by Peleus and abandoned both father and son in a rage