Medusa

The evil Medusa is the main antagonist in the ride Journey to Atlantis, in SeaWorld San Diego & SeaWorld Orlando.

SeaWorld San Diego
The guests sail to Atlantis, an unknown city, when they encounter Medusa, an evil war women-turned-gorgon. Medusa tries to kill them, but they escape her.

They then sail from Atlantis to the volcano where Medusa lives. They fight her in a final battle, and destroy her.

SeaWorld Orlando
The guests see Medusa disguised as a mermaid, and she becomes their guide. A few moments later, they see her killing Alexander the Great's wife, and Medusa reveals that she is really a war women-turned gorgon, showing her true form. She chases them to her lair, a volcano. They try to escape the volcano, but Medusa is hot on their heels. The guests then finally escape to Atlantis.

The guests arrives back into the volcano, to destroy Medusa once & for all. She battles them, but she yells "NO! NO! NO!" as the guests finally destroy her.

Trivia

 * Medusa thinks she's a godess.
 * Medusa does not appear on the Journey to Atlantis at SeaWorld San Antonio.
 * She is one of the most evil ride villains of all time.