“Optimistic” means having a positive outlook or expecting good things to happen. Some antonyms for “optimistic” are “pessimistic”, “cynical”, and “gloomy”.
“Pessimistic” implies having a negative view and expecting bad outcomes. For example, “While she is always optimistic about the future, he is pessimistic and sees only problems ahead.” This shows the contrast between an optimistic attitude and a pessimistic one.
“Cynical” suggests a distrustful and skeptical view of human nature and motives. “Her once optimistic view of people has been replaced by cynicism after a series of disappointments.” Here, cynicism stands in opposition to optimism as it indicates a lack of hope and belief in the goodness of others.
“Gloomy” refers to a sad and depressing mood or outlook. “The weather was gloomy and so was his mood, far from his usual optimistic self.” This highlights the difference between being optimistic and having a gloomy perspective.