Achilles' character.

Achilles didn't do what Agamemnon wants him to do, but he instead refused to obey Agamemnon and play he's lyre in his tent, after being insulted by Agamemnon. Agamemnon wanted Achilles to bow down everytime he went to the King's tent, which resulted an arguement between them. Achilles is known to be great warrior among the soldiers of Achaeans who didn't like the treatment of Agamemnon that makes Achilles to refuse to go in front of the line. Agamemnon sent his emissaries loads of  peace offerings for Achilles but this didn't impress Achilles and told to them, "I'd rather go home and live in peace instead of going to the war with Agamemnon's soldiers "

Achilles showed stubborness when he decided not to continue to go in front of the line cause his skills are far more superior than anyone. And he is bound to fight with the Achaeans army in the disposed of King Agamemnon.

Achilles is a great warrior. He has superhuman strength and has a close relationship with the gods. He's the mightiest man among the Achaean army. He cannot control his pride. The way Achilles acted when he refuse to follow the orders of the king that led him to abandon his fellow soldiers and even pray that the Trojans will kill them. By choosing his personal faith, Achilles will be remembered to be one of the great warriors ever lived with pride and honour.