mop up the floor with
Also, wipe the floor with. Defeat thoroughly, overwhelm, as in The young boxer said he was sure to mop up the floor with his opponent, or I just know we'll wipe the floor with the competition. [Late 1800s]
The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.