The term "be fiasco" refers to a situation that has ended in complete failure or disaster. However, there are several antonyms that describe the opposite of such a scenario. Some of these antonyms include success, triumph, achievement, victory, and accomplishment. Success refers to achieving a desired outcome, while triumph is used to describe a great victory or accomplishment over a challenge or obstacle. Similarly, achievement and accomplishment both entail successfully completing a goal or task. In essence, any positive outcome that leads to satisfaction or pride could be considered an antonym of "be fiasco.