The only way, I think, is to have a dragon with endeavour, like axew, drampa or Jangm-o (I'm not sure, but maybe in Agate Circus someone can teach it), an item which works like sturdy, and a move with high priority. Unfortunately, even if axew, drampa and jangm-o can learn endeavour, they don't have a move with high priority.
Or you can get a large amount of cotton candys by trade and wait for Garchomp to end every move it knows. Then he'll die for struggle.