In the Iliad, the Trojan prince Hector curses him as he dies to Achilles, stating that the younger prince Paris (the dude that caused the entire Trojan War) would pierce him in the heel with an arrow. Some versions state the arrow struck because Apollo guided it, due to him hating Achilles, or that it was poisoned, but the general idea is that no matter what, Paris was a coward and killed him a cowardly way, and thus didn't deserve to be considered heroic or valorous.