The head of the executive department could be called the Executive Department Head, supervisor, manager, etc.
Executive Aggreement
The president of the United states
In the US it would be the governor.
Exectutive agreement
The head of a federal executive department is usually called "Secretary", except that the head of the Justice Department is the Attorney General.
Chief accountant
The head of departments are usually called director or manager.
Typically, the department that deals with personnel issues is called "Human Resources".
Washington
Mayor
Except for justice, the department heads are called Secretaries. The head of Justice is the Attorney General.
Except for justice, the department heads are called Secretaries. The head of Justice is the Attorney General.