But, 'beast' is so harsh. I prefer Maleficent.
Maleficent was an evil witch who lived in the fairytale land, and who presumably had a grudge against Aurora's family. At some point, Maleficent was granted access to the Dark Curse by one of her only friends, Queen Regina, traded for her famed sleeping curse.
When said sleeping curse failed to have the results Regina expected, she demanded to be given the Dark Curse back, and a battle ensued between the two witches, one which Regina won.
When the curse was set in motion, Maleficent became trapped in Storybrooke, Maine, in a form rather different to that of the curse's other victims: her dragon form.
Cause of Death: Sword Impaled by Emma
Episode of Death: "A Land Without Magic"
Origin: Enchanted Forest
Portrayed By: Kristin Bauer van Straten
First Appearance: "The Thing You Love Most"
Latest Appearance: "New York City Serenade