merciless
adjective disapproving uk/ˈmɜː.sɪ.ləs/ us/ˈmɝː.sɪ.ləs/
C2 冷酷无情的，残忍的，毫无怜悯之心的
having or showing no mercy
There are reports of merciless attacks on innocent civilians. 有报道说无辜平民受到了残酷无情的攻击。
There was no shelter from the merciless (= very strong) heat. 滚滚热浪下人们无处躲避。