The term "most nullifying" refers to something that has the strongest potential to negate or cancel out something else. Its antonyms would describe things that have little to no effect or impact. Opposites of most nullifying could be "least influential," "ineffective," "inept," "inefficient," "unsuccessful," or "ineffectual." These words suggest an inability to produce a significant effect or to negate something else. For example, a dull knife would be the opposite of a sharp knife, just as "least influential" is the opposite of "most nullifying." In short, antonyms for "most nullifying" would refer to things that are weak, inadequate, or ineffectual, as opposed to something that is potent or powerful.