Yeah great movie but it didnt follow the story in entirety...
Patrocles whom Hector killed was not Achilles cousin, but his best friend...
Patrocles wearing Achilles' armour ripped the Trojan army solely riding on the fear and awe that Achilles armour generated until he was felled by Hector...

Another main deviance was that Hector didnt just kill Patrcoles, Hector actually mutilated Patrocles body beyond recognition when he found out that the greeks used Achilles "Fear Factor" to cause commotion in Trojan ranks..He also rips Achilles armour and take its home...Its the half naked mutilated body of his best friend that actually enrages Achilles who then rejoins the Trojan war, his difference with the Greek emperor, Argememon not withstanding...Achilles had to get a new armour to fight the rest of the war...

But ofcourse in general the characters of the 2 heroes where aptly shown...Achilles as the selfcentered, sometimes noble but always arrogant warrior whos destined never to lose in a battle and Hector, the great leader and price of Troy...