Extremes refer to the furthest or the greatest degree of something. When talking about synonyms, one can use words such as maximum, minimum, peak, lowest, highest, ultimate, utmost, and radical. Maximum refers to the highest possible level of something. Minimum is the opposite of maximum, it is the lowest level possible. Peak means the top or highest point of something. Lowest refers to the bottom or the lowest level of something. Highest means the top or the highest level of something. Ultimate refers to the highest or the final stage of something. Utmost refers to the highest degree of something. Radical refers to an extreme or drastic change or reform.