>>44756910I would personally recommend Precipice Blades.
Precipice Blades is also a multi-target move, but it only hits the opponents, so there's no worries about damaging your other Pokemon, and it has more power than Earthquake.
But since Precipice Blades is the signature move of Groudon, and you might not have a Groudon, High Horsepower is another good option because it's a single-target move (the strongest single-target Ground move) and doesn't have its damage reduced by being in a double battle.
