Beat The Pants Off Meaning

(transitive, idiomatic) To thoroughly and decisively defeat someone, either in a physical fight or, figuratively, in a competition.

Example: 1987 Sept. 6, Bernard Weinraub, "Reagan Tells Congress to Shun Protectionism," New York Times (retrieved 16 Aug 2012):
  American workers can outcompete and beat the pants off anybody, anywhere.
2001 June 24, Janice Castro, "Business," Time:
  Their counterparts in Canada, Europe and Japan made less than half as much, sometimes while beating the pants off them in the marketplace.