酷 ⇒
酷 kù, ruthless/strong (e.g. of wine)/(loanword) cool/hip
残酷 cánkù, [殘酷], cruel/cruelty
冷酷 lěngkù, grim/unfeeling/callous
酷刑 kùxíng, cruelty/torture
严酷 yánkù, [嚴酷], bitter/harsh/grim/ruthless/severe/cut-throat (competition)
酷爱 kùài, [酷愛], to be keen on/to have a passion for
酷热 kùrè, [酷熱], torrid heat
残酷无情 cánkùwúqíng, [殘酷無情], cruel and unfeeling (idiom)
酷似 kùsì, to strikingly resemble
酷暑 kùshǔ, intense heat/extremely hot weather