Of the 3 levels of government in the us which is supreme over the others ?

This is a very subjective question but probably the Executive Branch

Explanation:

The Executive Branch has the power to choose judges so that basically gives them control over the Judicial Branch.  They can veto bills from Congress which gives them some control over the Legislative Branch.  Presidents are also Commander in Chief so they are in charge of the military.

Executive Branch

Explanation:

The executive branch carries out and enforces laws. It includes the president, vice president, the Cabinet, executive departments, independent agencies, and other boards, commissions, and committees.