From the very beginning of the poem, the character Achilles is one of the major foci of the story. His actions of lack of actions have enormous effects upon how the plot unfolds. Starting with the fight with Agamemnon and his withdrawal from the battle, to the death of Patroklos, and finally to the slaying of Hektor, Achilles and his emotions decide the fate of many Greek and Trojan warriors. It is his struggle against his anger, pride, loyalty, and love that make this poem one of a tragic nature, rather than just a gruesome account of a war. Although the reputation of Achilles claims him to be the perfect warrior, strongest of the Greeks, the poem spends more time on the man than on his reputation. I think the most obvious presentation of this occurs in the final book and is consistent with the character earlier in the poem.
I believe the most speculation about inconsistencies in Achillesí character would center on his savageness towards the Trojans, especially Hektor, after the death of Patroklos, and his sensitivity towards Priamís plea for his sonís body. It could be considered odd that Achilles is so understanding to Priam and the burial of Priamís son, when not that long ago Achilles was dragging the body of Hektor around the grave of Patroklos. This is the same corpse that Achilles vowed to feed to the dogs, the man who slew Achillesí dearest companion and led him to swallow his pride and return to the battlefield. I believe that this is not the same Achilles we saw prior to the death of his loving companion Patroklos. After Patroklos rode off into battle and was cut down by a mix of divine intervention and Hektor, grief and the desire to revenge the death of Patroklos consumed Achilles. Thus I feel his behaviour throughout these books where he is moved to battle is a function of his personality acting under tremendous pain and grief.
A better place to view Achilles is in the first book. The argument that Achilles presents at the beginning of the poem is very rational and heartfelt and surprises me that it took ten years for it finally to get mentioned. Achilles sheds light on the fact that all the Greeks are at Troy to fight over the pride and honour of Agamemnonís brother and is brave enough to stand up to the king and call him greedy and selfish. His lack of hatred towards the Trojans as a people is easily seen in his statements about how the people of Troy had never wronged him prior to the conflict. This sympathy for the Trojans comes back in the final book where Achilles promises Priam twelve days of cease-fire to mourn and bury Hektor. This action, as I have said earlier, seems strange when set so close to the death of Hektor, but in context with Achilles earlier, it is not hard to believe that he would do this. Achilles is a very passionate man, not just in warfare but in his feelings for his close friends and family and for people in general. Of all enemies, the Trojans are very hard not to like or at least be pitied. All the Trojans, except for Paris, are good-hearted family men who are defending their homes, wives, and kids from destruction just because foolish Paris refuses to give up his beautiful wife. I think author intends that reader feel sorry for the people of Troy. After the last book, the reader is left with an image of Achilles that is hard not to respect. Achilles graciously puts away his anger and welcomes the father of the enemy, showing his skill of hospitality, which was also seen in the welcoming of the embassy from Agamemnon. Then Achilles mourns with Priam, returns the corpse of Hektor, and offers the king relief from fighting so the people can properly bury Hektor. This is a very mature Achilles we see here. I think the reason for him being slightly more mature in this last book than in earlier books is not to do with the book being a later addition, but rather that Achilles grows up.
Achilles is a man of noble principles all throughout the poem. His argument with Agamemnon is a testament to that. When Achilles refuses the gifts of Agamemnon that were offered to him, Achilles shows that his principles rank higher than desire for fame on the battlefield. The only point at which I think he compromises his principles is when he allows Patroklos and his men to go off and fight and refuses to go himself. I think that, at that point in the story, he is putting foolish pride before his loyalty and love for his friend. This is the tragedy of human flaws and the shortsightedness that goes along with anger. This scene in the story is one of transition, not just in the turn of the war, but in the maturing of Achilles as he finally begins to follow the path of his destiny. He chooses a fate of death over dishonour, truly a heroís decision. Then after he avenges his fallen companion and the blood lust has left his system, he shows his growth and new understanding of loss in the touching scene with Priam. The last book is not an all new Achilles, but instead the same Achilles who is perhaps wiser due to the lessons that only death can teach.
The tragedy of the Trojans is that they are good people who are destined to fall to the Greeks because of one woman, but the main tragedy centers on Achilles. Forced out of battle by an argument with a despicable Agamemnon, forced to linger and watch his comrades die, and, finally, forced into a destiny of early death and the loss of his dearest friend. Yet, as tragic as his character is, Achilles still is human enough to grant an old man a wish, though it hurts him to do so. Book 24 is not about Achilles the fighter or the hero, but rather the noble man that he is all throughout the poem.