What are examples of irony in Candide?

Candide and Cundegonde's relationship is packed with irony. For one, they start out as idealistic lovers who are hopelessly devoted to one another. Candide goes on a quest to reunite with Cundegonde, holding her in his mind as a symbol of purity and goodness. Even in the utopian world of El Dorado, he is unhappy without her beside him.
However, when Candide finally has the chance to marry Cunegonde at the end of the novel, she has been forced to become the mistress of several men, has lost her beauty, and had become a more irritable person after all the horrible things she has been through. She is unable to remain an ideal because she has seen too much cruelty in the real world outside her privileged sphere.
The irony comes from the way the "love conquers all" ending is subverted: Candide marries the girl of his dreams, but she is no longer who she was at the beginning of the story. Cunegonde's development also satirizes Candide's optimism, showing how things aren't turning out as wonderfully as he thought they would. His disillusionment with his love parallels his disillusionment with the philosophy of optimism.