穷寇

hard-pressed enemy;fleeing routed enemy
～勿追never corner a defeated enemy; do not pursue an enemy who is desperate/宜将剩勇追～，不可沽名学霸王。(毛泽东诗《人民解放军占领南京》) With power and to spare we must pursue the tottering foe,And not ape Xiang Yu the conqueror seeking idle fame.(Mao Zedong’s poem Capture of Nanjing by The People’s Liberation Army)