Ursula- The Little Mermaid
Ursula is evil, vengeful, and flat out plagued by jealousy, which causes her to act like a jerk to Ariel. She is jealous of Ariel's beauty, her power, and her position of being a member of the royal family. Much like other fairy tales, Ursula is a demonic, Devil like figure that convinces the protagonist of one thing, while making sure they're oblivious of the consequences, which is truly despicable.