The word "intensest" is the superlative form of the adjective "intense," which means having a strong and powerful effect or showing great concentration or determination. An antonym of "intensest" could be "calmest," meaning showing or having a peaceful and quiet nature, or "mild," meaning not strong or severe. Another antonym could be "lackadaisical," meaning showing or having a lack of interest or enthusiasm. Additionally, "relaxed," "unaffected," or "unemotional" are also antonyms of "intensest." These words signify a lack of vigor, passion, excitement, or tension that characterize the intensity of a situation or experience.