The term "most hundred-proof" implies a strong and intense flavor or effect. Antonyms for this phrase can include weak, diluted, light, and mild. These words suggest a lack of strength or potency, which can be desirable in certain contexts, such as a refreshing drink on a hot day. The opposite of "most hundred-proof" can also describe a lack of intensity or excitement, suggesting something boring or unremarkable. Ultimately, the choice of antonym depends on the context and desired effect, whether it's a heavy and full-bodied drink or a light and refreshing one.