Chief Warrant Officer 2
Sergeant Major of the Army is the highest rank NCO.
Anyone in the US Army can lose their rank - in the late 1990s, the Sergeant Major of the Army was demoted. It's not as easy for an SFC to lose their rank as, say, a Specialist or Sergeant, but it can happen.
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.
In the US Army, there's two ranks - Specialist, and Corporal. In the US Marines, it's just Corporal. The Specialist rank in the Army is not an NCO rank, whereas Corporal is.
Lieutenant Colonel.
captain
General of the Army.
Usually, a Captain.
In the US Army, a full bird refers to a Colonel, which is the rank between Lieutenant Colonel and Brigadier General.
General of the Army (five stars). However, this is a special rank used only in wartime. Currently, General (four stars) is the highest achievable rank.
His rank is Captain, his pay grade is 0-3.