The phrase "most cemented" refers to something that is firmly established or fixed. Its antonyms would be words that describe something that is impressionable, flexible, or unsteady. Synonyms for these antonyms include words like malleable, pliable, soft, supple, and variable. So, if something is not "most cemented," it could be described as "softly established," "lightly set," or "slightly solidified." To illustrate, one could say that a new relationship is not "most cemented" yet, as it is still in its early and flexible stages, allowing for growth and change in the future.