The principal antagonist is King Agamemnon, who abuses his power and betrays Achilles by stealing the warrior’s favorite war prize, the young maiden Briseis. Achilles sees Agamemnon’s act as both a personal betrayal and a sign of the king’s failure as a leader. In the face of the intensity of Achilles’s rage and the Achaean losses that quickly accumulate once Achilles removes himself from battle, Agamemnon admits the error of his action and begs for the wronged warrior’s forgiveness. But Achilles proves unyielding in his grudge. Curiously, even as Achilles continues to insist on Agamemnon’s moral bankruptcy, the poet shows Agamemnon to be a fine leader who eagerly launches himself into battle with his soldiers. By joining the front lines of the fight, Agamemnon demonstrates his willingness to win his own glory in battle, which stands in opposition to Achilles’s critical assessment of the king. Clearly, then, Agamemnon isn’t as thoroughly corrupt as Achilles seems to think.
Even though Achilles positions Agamemnon as his chief antagonist, Achilles’s own unrelenting rage proves to be his worst enemy. When he removes himself from battle and pledges to refrain from fighting until the war reaches his out-of-the-way camp, Achilles puts himself—and his fellow Achaeans—in grave danger. In order for the war to reach Achilles’s camp there would have to be great losses for the Achaeans since the Trojans would have to overtake all the other Achaean camps and set fire to their ships. Achilles’s rage blinds him to this reality even when others point it out to him. In Book 9, for instance, Agamemnon sends an embassy to Achilles, offering an outrageously generous gift if he will relent and return to the front lines. The great tactician Odysseus begs Achilles to let his “heart-devouring anger go,” and the old warrior Phoenix passes judgment on his surrogate son, saying: “It’s wrong to have such an iron, ruthless heart. / Even the gods can bend and change.” Even so, Achilles persists in his refusal to fight, endangering himself and his brethren alike and ultimately leading to the death of his most beloved friend, Patroclus. In this sense, Achilles’s rage is the great antagonist of the poem, far surpassing the conflict instigated by Agamemnon.