The antonyms for the word "under-valued" are "over-valued," "precious," and "cherished." These words express the opposite meaning of "under-valued," which refers to something or someone that is underestimated, downplayed, or not given enough recognition or appreciation. "Over-valued" signifies something or someone that is overrated, overpriced, and overestimated, while "precious" and "cherished" connote something that is highly valued, treasured, and dearly loved. Using these antonyms in a sentence can alter the meaning and tone of the sentence, making it more positive, negative, or neutral depending on which antonym is used.