William Afton

Trivia
His actual motivation for killing the children is still a mystery, although many people assume he did for his own enjoyment, or as part of an experiment to create life from the dead.
 * Freddy Fazbear’s Pizzeria Simulator implies the latter, as a blueprint reveals the Scooper’s purpose; to transfer remnant, a substance that gives a soul its ability to remain after death, into the animatronics.
 * Furthermore, a minigame accessed during the Midnight Motorist arcade game features a man depicted by a yellow sprite, who is shown to be abusive to his son. The "yellow man" is speculated by many to be William's father, and Michael and Elizabeth's paternal grandfather, causing many to believe that William's child murders stem from his own abusive childhood at the hands of his father.
 * A theory suggested that, like his son Michael, he was scooped and possessed by his other son.
 * He starts off as the main antagonist of the series, however, this is only a guise to hide the true main villain.