残酷【ざんこく】
cruel, brutal, ruthless, merciless, inhuman
冷酷【れいこく】
cruelty, coldheartedness, relentless, ruthless
酷暑【こくしょ】
intense heat, severe heat
酷評【こくひょう】
severe criticism, sharp criticism, scathing criticism, diatribe, panning
酷使【こくし】
exploitation, overuse, abuse