Antonyms for "most flabbergasted" include "unfazed," "composed," "level-headed," "calm," "collected," "unperturbed," "unimpressed," "unmoved," "unruffled," and "stoic." These words refer to a state of being unaffected, cool and calm, especially under stressful situations. An individual who is not flabbergasted is able to maintain their composure and act rationally. These antonyms are useful in situations where it is necessary to stay calm and make decisions that require a clear mind. Mastery of one or more of these antonyms can help prevent the harmful effects of stress and anxiety, improve decision-making skills, and enhance one's overall cognitive and emotional well-being.