After Michael Scott left Dunder Mifflin towards the end of season 7, 7 people took the role of Regional Manager:
DeAngelo Vickers (in a not great cameo from Will Ferrell)
Dwight Schrute, acting manager
Creed Bratton, acting manager
Robert California (left on his first day)
Andy Bernard
Nellie Bertram (an entirely unnecessary addition to the cast)
Kevin Malone (he won it for an hour in the episode “Roy’s Wedding” from season 9)
and finally back to Dwight Schrute (for real this time)