The term "most immalleable" implies that something is resistant to change or alteration. So, its antonyms would be the words that express flexibility, pliability, or malleability. The opposite of "most immalleable" can be coalesced into a list of terms such as flexible, malleable, supple, pliable, ductile, elastic, adaptable, lenient, pliant, and resilient. For instance, a material that can be easily molded, stretched, or compressed is considered malleable, whereas something that cannot be altered or shaped adequately is immalleable. Therefore, the antonyms of "most immalleable" embody elasticity and adaptability and showcase the opposite of being rigid and inflexible.