Most attenuated refers to something that is weakened or thinned out to its maximum degree. The antonym for most attenuated would be the phrase "most concentrated" which refers to something that is made stronger or denser. Other antonyms include "thickened," "strengthened," "intensified," "compacted," "consolidated," "strengthened," "dense," "potent," and "exaggerated." These words describe something that is more concentrated, thicker, or bolder in essence. While most attenuated indicates a loss of strength or thickness, these words speak to an increase in such attributes, and may be used in contrast to "most attenuated" to provide further context or clarification.