Thersites is the ugliest man who came to Troy — bow-legged, lame, cave-shouldered, with a pointed head sparsely tufted — who alone rails at Agamemnon in the Iliad's assembly until Odysseus beats him with the sceptre and the host laughs. Later epic makes him son of Agrius of Calydon, cousin of Diomedes, and victim of Achilles after he insults the dead Amazon Penthesilea. Homer never names his father, leaving him marked as a commoner among aristocratic heroes.
Adapted from Wikipedia, "Thersites" · CC BY-SA 4.0
I.Family and Calydon
The Iliad omits his father's name, which may mark him as a common soldier rather than an aristocratic hero. A quotation from the lost Aethiopis names his parents as Agrius of Calydon and Dia, daughter of Porthaon — making him a first cousin once removed of Diomedes.
Euphorion ties his disfigurement to the Calydonian Boar Hunt: assigned to watch for the boar, he fled to safer ground; Meleager pursued him, and he fell from a cliff. Apollodorus has Thersites and his brothers overthrow Oeneus for their father Agrius; Diomedes later restores Oeneus and slays the brothers, while Thersites escapes.
II.Iliad Book II
Homer describes him at length though his role is brief. Vulgar and disorderly of speech, he rises in assembly and attacks Agamemnon in Achilles's own charges — greedy, cowardly, a hoarder of prizes. Odysseus rebukes him, threatens to strip him naked, and strikes his back and shoulders with Agamemnon's sceptre until a bloody welt rises and he sits weeping while the rest of the army laughs.
He does not reappear in the Iliad. Robert Graves suggested Homer made him ridiculous precisely so that justified protest could remain in the poem without the poet seeming to endorse it.
III.Death and later literature
In the lost Aethiopis Achilles kills him — by one account for tearing out the eyes of the Amazon Penthesilea whom Achilles had just slain; Quintus of Smyrna has him insult Achilles for loving the Amazon, after which Achilles strikes him dead and must be purified on Lesbos. Diomedes, as cousin, is enraged by the killing.
Plato's Gorgias cites him as a soul curable in the afterlife for lack of might; in the Republic he chooses rebirth as an ape. Shakespeare makes him a scurrilous fool in Troilus and Cressida; Goethe's Faust and Sterne's Tristram Shandy likewise keep him as the type of abusive satire. Hegel's "Thersitism" named the pattern of voicing a crowd's protest through a figure no one need respect.