Which literary device contrasts the expectations of the characters with the actual outcome?

The chosen answer, irony, is the most appropriate literary device that highlights a contrast between expectations and reality. Irony occurs when there is a significant difference between what is expected to happen and what actually happens, often creating a surprising or thought-provoking effect. For instance, a character might prepare for a grand celebration, only to find that their plans are unexpectedly derailed, illustrating a stark contrast between their expectations and the outcome.

Foreshadowing, while it involves hints or clues about what may happen later in the story, does not inherently create a contrast between expectation and outcome. It serves more to build anticipation rather than to reveal a contradiction between what characters hope or believe will happen versus what actually transpires.

Flashback, on the other hand, is a narrative technique that allows a character or narrator to reflect on past events, providing background but not necessarily generating a dissonance between expectations and reality at the narrative's present moment.

Metaphor is a figure of speech that makes a comparison between two unrelated things, highlighting similarities but not directly addressing the relationship between expectation and actual outcomes.

In summary, irony effectively captures the essence of contrasting expectations with reality, making it the correct choice for this question.