The phrase "most olfactive" implies something that has a strong smell or odor. Antonyms of this phrase could include "odorless," "inodorous," "unscented," or "fragrance-free." These words describe a lack of smell or a subtle scent that is not overbearing. Another antonym could be "faint" or "weak," indicating a barely noticeable or mild odor. Alternatively, words such as "insipid," "bland," or "unappetizing" could also be antonyms of "most olfactive," as they suggest a complete absence of aroma and flavor. The context in which these antonyms are used will depend on the situation, sensory perception being described, and the intended meaning of the text.