The antonyms for the phrase "speaks highly of" include terms like "criticizes," "condemns," "censures," "rebukes," and "disapproves of." When a person speaks highly of someone, they are praising and complimenting them. Conversely, when someone criticizes or condemns a person, they are expressing their disapproval or dissatisfaction with their behavior, attitude or performance. The choice of words to describe someone has a profound impact, and antonyms can be useful in expressing various attitudes and emotions. Thus, using the right antonym can help convey a precise message about a person, circumstance, or situation.