Keep that girl out of sight and you and your daughters will have whatever you desire.
~ The Grand Duke
The Grand Duke is the secondary antagonist of the 2015 live action film Cinderella, based on the 1950 Disney animated film. Though originally seen in the 1950 film & its sequels as a hero, he is shown having a far more sinister & antagonistic role, secretly working with Lady Tremaine.
As he is more focused for the future of the kingdom rather than respecting the King or Prince's wishes, the Grand Duke secretly promises Kit to a specific princess, a statement to which Lady Tremaine overhears during the ball. Following the death of the King and Kit's inheriting the throne, the Grand Duke is given the order that every maiden will try on the glass slipper.
Eventually, the Grand Duke soon learns about the identity of the mystery girl who danced with Kit after Lady Tremaine meets him. Lady Tremaine then offers to help with his problem by keeping this silent, and in return for her help, she will get to be a countess and her daughters Anastasia and Drizella will have proper husbands. The Grand Duke accepts the deal and takes the shattered shoe to Kit, hoping to persuade him to forget the mystery girl, but this makes Kit more determined than ever to find her.
The Grand Duke and the captain of the guards lead a mission to try the remaining shoe on all the maidens in the land, but it fits none of them. When they arrive at the Tremaine estate, the shoe fits neither of the stepsisters. The officers turn to leave, only to hear Cinderella singing through a window that the mice opened for that purpose. The Grand Duke tries to leave anyway, but one of the men reveals himself to be Kit in disguise and demands that the captain investigate the sound. Once Cinderella is revealed to be the mystery girl, The Grand Duke is last seen bowing down to both Kit and Cinderella for forgiveness along with Drizella and Anastasia. Though it may not be clear if he was forgiven or not, it's revealed that the Grand Duke was forever banished from the kingdom along with Lady Tremaine and her daughters for their act of treason.
He is the second iconic Disney hero to be depicted as a villain, the first being King Stefan and followed by King Louie.
The Grand Duke's original role is apparently given to the Captain instead.