George Washington without the slightest doubt. He created the Army, held it together in the most difficult times it has ever faced to this and led it to victory over the greatest power in the world. He never attempted to tell the civilian government what to do, never attempted to take over the government, and when he was elected President, he made sure to rule as a civilian and not as a General or a King. We have been blessed in critical times with other great military leaders but none carrying the load Washington successfully carried.
Listening to all the current Democrat candidates speaking and each one of them speaks as if they would be King and rule by fiat. None say they would ask Congress to pass legislation they just say they would do things like handing out money they do not have.