The term "pull fast one" typically refers to a deceitful or dishonest act, and as such, antonyms for this phrase would be words that connote honesty or straightforwardness. Possible antonyms could include "transparent", "honest", "reliable", "trustworthy", "straightforward", "aboveboard", "sincere", "forthright", "genuine", or "truthful." These words all suggest a person or action that is characterized by honesty and openness, rather than manipulation or deception. Using these antonyms can help emphasize the importance of integrity and ethical behavior, and serve as a reminder to always act with honesty and transparency.