How to say "cold-hearted" in Japanese

• 非情ひじょうCommon
  na-adjective, no-adjectiveCovers the harsher sense of 'cold-hearted': callous, unfeeling, even cruel. It suggests a lack of compassion that shows in ruthless actions or decisions, so it fits contexts of pitiless treatment rather than mere emotional distance.
  これらの気の毒きのどくな人々ひとびとは非情ひじょうな独裁者どくさいしゃのなすがままになっていた。↗

  These poor people were at the mercy of the cruel dictator.
• クールCommon
  na-adjectivePrimarily means 'cool' in the sense of calm, collected, and cool-headed; 'cold-hearted' is a secondary shading of that detachment. It is not the word for genuine cruelty or heartlessness, only for a stylishly composed, seemingly indifferent manner.
  彼女かのじょのクールな視線しせんに、俺おれはドキッとした。↗

  Her cool gaze made my heart skip a beat.
• 冷淡れいたんJLPT N1approx.Common
  na-adjective, nounDescribes someone who is emotionally cold, unkind, or heartless toward others — an attitude of indifference and lack of warmth. This is the natural choice when 'cold-hearted' means personally distant or unfeeling in dealings with people.

Use 非情 for ruthless cruelty, 冷淡 for emotional coldness and indifference, and 「クール」 only when calm, collected coolness shades into seeming cold-hearted.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 非情ひじょうcold-hearted
• 冷淡無情れいたんむじょうcold-hearted
• 薄情はくじょうunfeeling
• クールcool (i.e. calm and collected)
• 冷淡れいたんcold