The term "half-heartedness" refers to a lack of sincere commitment, interest or enthusiasm in performing an activity or taking a decision. When we speak of antonyms for "half-heartedness," we refer to words that convey the opposite sentiment. Some possible antonyms for "half-heartedness" include zeal, fervor, wholeheartedness, enthusiasm, passion, ardor, dedication, and commitment. These words suggest a strong desire, determination or passion to complete a task or undertake an action. For instance, "wholeheartedness" conveys a sense of total commitment and enthusiasm, while "passion" and "ardor" denote a deep interest and love for something. Antonyms for "half-heartedness" thus convey a strong, positive emotion towards the task at hand or the decision being made.