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] 摧折枯树朽木

镌金石者难为功,摧枯拉朽者易为力。——《汉书·异姓诸侯王表》