How to say "cold-blooded" in Japanese

• 無残むざんCommon
  na-adjective, nounCovers cold-blooded as 'atrocious, gruesomely merciless': it paints the deed or its aftermath as horrific and pitiable. It suits describing a savage killing or a victim's wretched end more than the killer's character.
• 残忍ざんにんCommon
  na-adjective, nounThe direct word for cold-blooded as 'brutally, mercilessly cruel': it characterizes a person, act, or crime as savagely cruel and unfeeling. Typical for a cold-blooded killer or a brutal, remorseless crime.
  かつて残忍ざんにんな王様おうさまがいた。↗

  Once upon a time, there lived a cruel king.

Choose 残忍 for cold-blooded cruelty as a quality of a person or deed; 無残 instead stresses how atrocious and pitiable the act or its outcome is, fitting gruesome scenes more than characterizing the doer.

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

• 無残むざんcruel
• 残忍ざんにんbrutal
• 血も涙もないちもなみだもないcold-blooded
• 冷酷無残れいこくむざんcruel and heartless