Antonyms for the word "most overzealous" would be something that signifies a lack of enthusiasm or excessive effort. Some possible antonyms could be indifferent, apathetic, disinterested, lackadaisical, unenthusiastic, half-hearted, or complacent. These words describe a lack of interest, passion or conviction towards a particular task or activity, unlike the term "overzealous" which defines someone who is excessively passionate, energetic, or enthusiastic. When used in a sentence, antonyms for "most overzealous" can convey a sense of moderation, neutrality or detachment, thus adding depth and contrast to the language.