The antonyms for "hast mercy" can be characterized by cruelness, harshness, and indifference. One antonym for "hast mercy" is "cruelty" which suggests an absence of kindness, compassion or mercy. Another antonym can be "unforgiveness" which implies a lack of willingness or ability to forgive someone's mistakes, offenses or wrong-doings. "Heartlessness" is also considered an antonym, which suggests an absence of warmth, kindness, and emotion towards others. Finally, "unsympathetic" can be considered an antonym, which suggests a lack of understanding, support, and empathy towards others in distress. Understanding the antonyms of "hast mercy" allows us to appreciate the importance of compassion, kindness, and forgiveness in contemporary society.