The antonyms for the phrase "were merciful" are "were cruel," "were heartless," and "were uncompassionate." When someone is cruel, they intentionally cause physical or emotional pain or discomfort to others. In contrast, being merciful means showing compassion and forgiveness to someone who has wronged you. Heartlessness is a lack of concern or empathy for others, while being uncompassionate means lacking sympathy or understanding for others' struggles or suffering. To be merciful, a person must possess qualities such as kindness, empathy, and forgiveness, and the opposite qualities result in cruelty and indifference towards others.