Ursula

Ursula was the sea witch who proposed the human deal to Ariel in the past.

Story
When Sora visits Atlantica to find Melody, Ursula is used as an illusion by her sister Morgana to waylay Sora and Ariel from their search. Sora and Ariel manage to slay the illusion before they continue their search.

In the final battle for the Disney Castle, Maleficent resurrects the sea witch, as well as other villains such as Jafar and others for the final battle. When the fight with Ursula begins, she admits that she used Ariel all along for her schemes but is killed by Sora with the help of Ariel, Rambo and Pocahontas.