Achilles was dipped into the Styx River by his mother.Everything but his ankle was dipped, andthis made him invulnerable everywhere except his ankle.
The Trojan War breaks out.
Achilles all grown up and destined to be a great warrior asks to join the Greek Army
Achilles kills the Trojans with ease
Achilles was dishonored by his commander in war, so he left the war. Achille's friend acted as Achilles to scare the Trojans away, but then he was killed. This angered Achilles, so he went and killed the Trojan (Hector) who killed his friend.
Achilles went to respectfully return the body of Hector who he killed outside of war to avenge his friend. He was shot in the ankle by a poison arrow while returning the body. Achilles died from his injury. His ankle was his only weakness.