1) Achilles was a demigod hero of Greek mythology and the central character of Homer's Iliad, known for his great strength and courage in battle. 2) Achilles' most notable act during the Trojan War was killing the Trojan prince Hector after Hector killed his friend Patroclus. 3) Achilles was killed when the Trojan prince Paris shot him in the heel with a poisoned arrow, the only vulnerable part of his body, giving rise to the expression "Achilles' heel."