big enchilada

Also, big shot or gun or wheel or enchilada. An important, powerful person; the boss. For example, She loved being the big cheese of her company; the big guns in Congress are bound to change the President's bill; you'd better not act like a big shot among your old friends; Harry was the big wheel in his class; and You'll have to get permission from the big enchilada. The first term dates from the late 1800s and its origin is disputed. Some think it comes from the Urdu word chiz or cheez for "thing," but others hold it plays on the English word "chief." Big gun is much older, dating from the early 1800s; big shot became very popular in the late 1920s, particularly when used for underworld leaders of gangsters; big wheel dates from about the same period. Big enchilada, often put as the big enchilada, is the newest, dating from the early 1970s.

The noun has one meaning:

Meaning #1: (informal) an important influential person
  Synonyms: big shot, big wheel, head honcho