Who implements Article III, Section 1 in the U.S. Constitution wherein "The judges, both of the supreme and inferior courts, shall hold their offices during good behavior..."?
If you mean who decides what is good behavior, congress does. Congress would impeach a judge if he/she needed to be removed.
With respect to federal judges, under Article I of the United States Constitution, the House of Representatives has the power to impeach, and the Senate the power to hold a trial to determine whether removal is appropriate. The House can impeach a judge with a simple majority vote. However, a judge may only be removed from office following a trial and a vote to convict by a two-thirds majority of the Senate. https://www.brennancenter.org/blog/impeachment-and-removal-judges-explainer