The word "mattest" refers to something that lacks shine or luster, often used when describing hair or makeup. Antonyms of "mattest" would include words such as glossy, shiny, polished, or gleaming. These words signify something that is highly reflective, with a bright and smooth finish. Another antonym could be radiant, which denotes something that emits light or displays a vibrant glow. If one is looking for a more nuanced contrast to "mattest," words like glistening or sparkly may fit the bill, as they suggest a shimmering quality that can catch the eye.