The word 'most transitional' refers to something that lies in between two stages, often implying a shift or change that is in progress. Antonyms of this word would be 'fixed,' 'stable,' 'durable,' or 'unchanging.' These words suggest a sense of permanence or immovability, implying that something is unlikely to change. Other antonyms could include 'static,' 'rigid,' 'unchangeable,' and 'inflexible.' These words emphasize a sense of rigidity, suggesting that something lacks flexibility or adaptability. The opposite of 'most transitional' is anything that is fixed, stable or unchanging, suggesting a state of permanence or inflexibility.