摧枯拉朽　

◎ 摧枯拉朽 cuīkū-lāxiǔ

[(as easy as) crushing dry weeds and smashing rotten wood;destroy sth.already in a state of ruin] 摧折枯樹朽木

鐫金石者難為功,摧枯拉朽者易為力。——《漢書·異姓諸侯王表》