Gwendolin "Gwen" Grayson, previously known as Sue Tenny, with the villain ID of "Royal Pain", is the main antagonist of the 2005 Disney live action movie Sky High, played by Mary Elizabeth Winstead.
Gwen went to Sky High the same time Will's parents did, but she was under the name of Sue Tenny. She invented The Pacifier, which has the ability to turn any living human (Or animal, possibly) into an innocent baby. She wanted to rule the world, so she quit school early and started on her evil plan. Unfortunately, Gwen didn't get very far on account of her plans getting ruined by The Commander (Steve Stronghold), American Boy (Mr. Boy), and Jetstream (Josie Stronghold). Gwen (Under the name of Royal Pain) got thrown into a nearby wall and her Pacifier exploded, turning her into a baby. Stitches took her in and raised her as his daughter.
About 16-17 years later, Gwen returned under the name, Gwen Grayson. She sought out Will Stronghold, the son of the Commander and Jetstream. She flirted with him to get him to take her to his house, there secretly stealing her Pacifier back that Steve and Josie had picked up and taken with them after Gwen's defeat years ago. Then a few days before Homecoming at Sky High, Gwen invited the Stronghold family to the dance as the guests on honor. Steve and Josie accepted, but Will stayed behind after dumping Gwen for being rude to Leyla, Will's best friend. Meanwhile, at the dance, Gwen revealed herself to be Royal Pain, the same Royal Pain The Commander had fought nearly 17 years ago. Chaos erupts, and everyone exept for Leyla, Zack, Regenta, Warren, Ethan, Ron Wilson, and Will (who had gotten picked up by Ron in his school bus when he figured out Gwen's plan.) get turned into babies. While there, Will's friends took out Penny, Lash, Speed, and Stitches, (Gwen's Henchmen) while Will handled Gwen. Will defeated Gwen, having figured out that he could fly as wll as be super strong, and kept the school from falling out of the sky by Gwen's hand.
Later, after everything was organized, and everyone was back to normal, Gwen and her henchmen were sent to detention. For how long, is unknown. They are eventually sent to prison.
Gwen hates being called "Daddy's Little Girl" by Stitches, by the way.
Trivia:
As Royal Pain, it is loosely adapted from Dragon Maleficent and Snake Jafar.