In Part 2, Chapter 31, Aziz imagines the possibility that Fielding was in the cave with Adela. He uses hyperbole to describe his perspective on this possibility as the "worst" example of treachery in Indian history:
The girl had surely been Cyril’s mistress when she stopped in the College—Mohammed Latif was right. But was that all? Perhaps it was Cyril who followed her into the cave. . . . No; impossible. Cyril hadn’t been on the Kawa Dol at all. Impossible. Ridiculous. Yet the fancy left him trembling with misery. Such treachery—if true—would have been the worst in Indian history; nothing so vile, not even the murder of Afzul Khan by Sivaji. He was shaken, as though by a truth, and told Hassan to leave him.
Hyperbole appears in the following sentence: "Such treachery [...] would have been the worst in Indian history." This is a great exaggeration of the truth. Fielding's presence in the cave would not have been the worst treachery in Indian history; it merely appears of great importance to Aziz because he was the one accused of violating Adela. Aziz also has a strange sort of friendship with Fielding and always wants to think the best of him. The possibility of his "treachery" drives Aziz to utter despair. Hyperbole gives emotional emphasis to this strange fantasy and lets the reader know how strongly it disgusts Aziz.