The Ringleader

The Ringleader is a minor antagonist in the 2014 Disney animated feature film, Big Hero 6. She is Yama's right-hand woman.

Big Hero 6
At the start of the film, the Ringleader oversees the illegal bot-fights in Good Luck Alley. When Hiro Hamada tries to enter, she and Yama initially scoff him off. When Hiro turns out to be loaded, Yama eagerly accepts. To the surprise of everyone, Hiro wins the match, and the Ringleader is last seen handing over his earned money before Yama intervenes.

Big Hero 6: The Series
In "The Bot Fighter'', the Ringleader returns as the overseer of the bot-fights. She is surprised to see that Hiro wants to re-enter, but nevertheless denies him entry on account of being blacklisted on Yama's orders. Before he can be thrown out, Hiro sneakily points out that a rematch between himself and Yama would draw in huge crowds. For the sake of extra profit, the Ringleader enters Hiro.

Trivia

 * The Ringleader's design resembles the Fujitas, a group of villains that served as Yama's henchmen in earlier versions of Big Hero 6.
 * In Big Hero 6: The Series, she is credited as Yama's Assistant.