Antonyms for the word "most heart-rending" would be words such as joyful, uplifting, happy, delightful, and fulfilling. These words represent feelings of happiness and contentment, rather than the sorrow and pain associated with heart-rending situations. Joyful would represent a feeling of happiness and excitement, while uplifting would represent the positive emotions that can come from overcoming a difficult situation. Happy and delightful would represent feelings of joy and satisfaction, while fulfilling would represent a sense of accomplishment and purpose. These antonyms offer a stark contrast to the anguish and despair associated with the term "most heart-rending.