Umm Madaura XL (Magi)

Umm Madaura was a villain in the anime Magi who used a unique artifact that could control children. She took in children who were abandoned and even kidnapped other kids to form a league of underaged thieves. She tries to control the main characters but is unable to and is captured by the government when she attempts to escape. People of the city find her as she's dragged off and attempt to beat her to death until one of her previously mind controlled children intervenes. Despite Madaura praising the child, he raises his sword and decapitates his adoptive mother revealing he was no longer under her control.