cruel and heartless; merciless; implacable
A yojijukugo describing a person or action that is utterly cold-hearted and devoid of compassion. Stronger and more literary than 冷酷 alone.
He treated his subordinates with a cruel and heartless attitude.
その冷酷無情な決定に皆が反発した。
Everyone opposed that merciless decision.
冷酷 means 'cruel' or 'cold-hearted' and is more common. 冷酷無情 is an intensified, literary yojijukugo emphasizing complete lack of mercy.
無情 means 'heartless' or 'unfeeling'. 冷酷無情 combines both cruelty and heartlessness for a stronger effect.
A yojijukugo composed of 冷酷 (cold-hearted, cruel) and 無情 (heartless, unfeeling). The combination intensifies the meaning to 'utterly cruel and merciless'.