The antonyms for "has mercy on" are "hard-hearted," "cruel," "unsympathetic," "cold-blooded," and "pitiless." These words describe someone who lacks compassion, empathy, or sympathy for others. They are indifferent to the suffering of others and show no mercy, kindness, or leniency. Such people often act in a callous or ruthless manner, causing harm or pain to others without regard for their feelings, needs, or welfare. In contrast, those who "have mercy on" others are kind, compassionate, and understanding. They offer forgiveness, help, and hope to those in need, and treat others with dignity, respect, and love.