The phrase "with all heart" expresses a sense of enthusiasm, sincerity, and emotional investment towards someone or something. Antonyms for this phrase would convey a lack of interest, insincerity, or hesitancy. Words such as "half-heartedly," "indifferently," "halfway," "lukewarmly" or "coolly" could be considered.
Using antonyms for "with all heart" may indicate a lack of trust, affection, or passion. When you do something with all your heart, it conveys a sense of dedication and commitment, as well as a range of positive emotions. However, using antonyms may indicate negative feelings such as apathy or disinterest. Therefore, it is essential to use words carefully and thoughtfully to convey the intended meaning clearly.