The term "most slithering" implies a movement that is smooth, undulating, and sinuous. Antonyms for this phrase could refer to movement that is abrupt, jerky, clumsy, or rigid. The polar opposite of slithering could be described as convulsive, spasmodic, awkward, or clumsy. Alternatively, antonyms could focus on the qualities that make slithering unique, such as its smoothness and gracefulness. Words like clunky, mechanical, or robotic could effectively describe movements that lack the fluidity and finesse that are a hallmark of slithering. Ultimately, the antonyms for "most slithering" would depend on the context and the desired effect of the description.