Barbra Streisand (South Park)

Barbara Streisand is a real-world actress/singer who, although not villainous in reality, featured as the chief antagonist of South Park's "Mecha-Streisand" episode.

Depicted as a power-mad supervillain Streisand sought a powerful artefact by which to transform herself into a powerful monster and take over the world, to this end she tracked the object down to the town of South Park and began to pursue the boys: who wouldn't give her the object.

After a few attempts to retrieve the object Streisand kidnapped the boys and tortured them with her singing voice until they surrended the object to her - at which point she transforms into the titular Mecha-Streisand, a parody of Mechagodzilla.

Mecha-Steisand proceeds to go on a rampage until she is defeated by a large cast of other celebrities that have super-powered forms of their own (poking fun of Japanese monster movies).