The word "keenest" can be replaced by some synonyms that express the same meaning. Among them, we have "sharpest," which refers to something that is highly perceptive or quick-witted. Another synonym that can replace "keenest" is "most acute," which means having a finely-tuned sensitivity or awareness. Additionally, "intense" can also be used as a synonym for "keenest," as it describes something that is passionate or deeply felt. Other possible synonyms for "keenest" include "eager," "enthusiastic," and "ardent," all of which convey a sense of intense interest or dedication. Ultimately, the choice of synonym for "keenest" depends on the context in which the word is being used.