To behave mercilessly is to act without showing pity or sympathy, like a bully who torments other kids or a basketball team that beats the opponent 125 – 0. Whenever possible, it’s best to avoid people who act mercilessly.

When you show mercy, you're kind and empathetic. Without any mercy, you’re merciless, and when you act this way you act mercilessly. You show no pity! Some big brothers kid their little sisters mercilessly, and a judge who gives the maximum sentence for a minor crime has ruled mercilessly. Mercy is at the root of mercilessly, from the Old French merci, which means both "thanks" and "pity." If people act mercilessly, tell them thanks for nothing!

Definitions of mercilessly
  1. adverb
    without pity; in a merciless manner
    “he was mercilessly trounced by his opponent in the House”
    synonyms: pitilessly, remorselessly, unmercifully
Word Family

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