The Office of Personnel Management (OPM) which oversees the hung, training and sanagement of more than two

million federal employees is most likely associated which branch of the federal government?

The Office of Personnel Management (OPM) which oversees the hung, training and management of more than two million federal employees is most likely associated with "executive branch" of the federal government.

Explanation:

The "Pendleton Civil Service Reform Act of 1883" formulated the "United States Civil Service Commission" which was further on 1st January 1979 replaced by the "Office of Personnel Management (OPM) " as permitted by the "Civil Service Reform Act of 1978" with the motto of "recruiting, retaining and honoring a world-class force to serve the American people".

OPM is an independent organization categorized under executive branch of United States Federal Government and responsible for catering federal government's employees, retirees and their dependents from retirement benefits (CSRS/FERS, excluding TSP), life insurance (FEGLI), federal HR policy, healthcare (FEHB), oversight and support.