Garchomp! Got locked into a battle w/Cynthia in Platinum and got her down to 1 pokemon which was Garchomp and she wiped out my whole party of 6 pokemon with Garchomp alone. Everytime I attacked she got the first hit and killed my pokemon in 1 hit everytime. It was a dig move or something and I have yet to find out what that move was. He dug into the ground then popped up.