Officers out rank all enlisted personnel. So, it would be an officer. The third highest would be a Lieutenant General (O-9). That's assuming there's an 0-11, General of the Army that is active, which it isn't all the time. In that case it would be one rung lower, Brigadier General (O-8).
Sergeant Major of the Army is the highest rank NCO.
Field Marshal is the highest military rank in Pakistan Army.
The highest two-star army rank that one can achieve is Major General.
General
Imperator
General
Sergeant Major of the Army
In the US Army, General.
The highest Non-Commissioned Officer rank in the US Army is Sergeant Major of the Army. The current SMOA is Kenneth O. Preston.
General of the Army- 5 stars, arranged in a circle.
The highest rank is Field Marshal, currently held by Queen Elizabeth's husband, the Duke of Edinburgh. It is a purely ceremonial role. Following that is the rank of General which is held by the Chief of the Defence Force (a role that rotates through the heads of the three services) and then Lieutenant General. Therefore if the current Chief of the Defence Force is from the Army then the highest Army rank is General, otherwise it is Lieutenant General.
George Washington's highest military rank was commander in chief of the Continental Army.