The phrase "ring leader" refers to a person who leads or organizes a group, often in a negative or mischievous way. They are like the boss or captain of their group, influencing others to do certain things or follow their ideas. Full definition
The very evil ring leader of the posse Raymond Cobb (Jackie Earle Haley) was horrifically confrontational, and the scene turned into a bloodbath, with Isaac narrowly escaping, returning to his family and quickly saying goodbye. (cinemanerdz.com)
That's right, the next installment in the Ocean's franchise will be the latest film to do the gender - swapping thing, with Bullock taking over as ring leader. (news.avclub.com)
The syndicate ring leader's arrest came on the heels of tip - off and intelligence which incited the police to monitor his movement. (nigeriapoliticsonline.com)