Final answer:
Winston's greatest fear is rats, which is used to break his spirit in Room 101 by the Party in the novel '1984'.
Step-by-step explanation:
Winston’s greatest fear is rats, a phobia that is exploited against him during his time in Room 101, where the Party subjects him to psychological torture. The fear is so intense that it eventually breaks his resolve and leads to him betraying his deeply held beliefs and his loved one, Julia. In George Orwell’s novel 1984, the exploitation of Winston’s deepest fear emphasizes the extreme measures totalitarian regimes are willing to use to maintain power and control over individuals.