Cressida already had a bad reputation by the time Shakespeare retold her story in his very bitter play about war, politics, lust and the destruction of rightful order. In Shakespeare's version of Troilus and Cressida, Cressida is a whore, her uncle Pandarus is a bawd, Troilus is a fool and General Ulysses (Odysseus) cruelly manipulates Achilles in an attempt to control him, because Achilles, full of his ancient heroic arrogance, refuses to recognize his proper place in the hierarchy of the army.
Ulysses is in many ways the most interesting character in the play, and his speech on Degree is at the center of it. He argues that when people do not behave according to their proper ranks in society, the order of society falls apart and people are only ruled by their animal appetites. Chaos is the inevitable consequence of the breakdown of social order. Unfortunately, Ulysses does not seem to persuade anyone with his theory of social order, and the war goes on, and Troy must fall, as it always has.