Antonyms for the word "under rated" include "overrated," "highly acclaimed," and "well-regarded." These terms suggest that something is highly valued and respected by others, perhaps even to the point of being considered a classic or a masterpiece. Other antonyms might include "popular," "beloved," or "admired," all of which convey a sense of widespread approval and appreciation. In contrast to "under rated," which implies that something is not getting the recognition it deserves, these words indicate that something is highly regarded and highly valued by a large number of people.