Revan. The Guardians have no training against the Force. They are also slower, in terms of reflexes and physical movements. Revan throws his lightsaber to cut one down, Force chokes another, mind controls one, uses telekinesis to kill another, etc. He was a brilliant strategist and and he can use Force Sense to find out each Guardian's personal weaknesses. Hell, he can even buff himself with Force Aura, Speed, etc. Or he can use Force Wave to knock them all down, or Lightning to fry them all at once.