What final sin is punished in the ninth circle of Hell?

The ninth circle of Hell, as depicted in Dante's Inferno, is specifically reserved for the sin of betrayal. This circle is characterized by extreme ice, signifying the cold and treacherous nature of those who have committed acts of treachery against their kin, benefactors, or country. Dante categorizes these sinners into different groups based on the severity and nature of their betrayal, with the most infamous among them being Judas Iscariot, Brutus, and Cassius.

In this context, betrayal represents a profound violation of trust, making it the most grievous sin in Dante's view. The punishment reflects the act's severity, as the traitors are encased in ice, further emphasizing their isolation and the coldness of their actions. This distinct punishment in the ninth circle starkly contrasts with the sins depicted in the other circles, where the torments vary widely according to the sin's nature, such as greed, pride, or lust. Consequently, the focus on betrayal in the ninth circle illustrates Dante's moral framework, which prioritizes the loyalty and integrity of personal relationships above other sins.