Cthulhu

Cthulu is a god of unknown origin (possibly an alien of some sort), originally created by H.P. Lovecraft and is used in "Coon 2: Hindsight". He was first seen on a News 4 broadcast. When DP (formerly BP) drill a hole in the Gulf and accidentally reaches another dimension, they attempt to rectify the problem by drilling on the moon to change it's gravitational pull on the Earth, hoping that this will solve the problem. However, all this does is make the problem a whole lot worse when it releases Cthulhu. As of "Coon 2: Hindsight", Cthulhu is expected to reign over the Earth in a dark period of around over 3000 years. He appears as a very large green monster with glowing orange eyes, massive wings and long spindly arms. He is tall enough to stand in an ocean and still tower over a DP oil rig. And in "Mysterion Rises" it shows that Cartman (dressed as the Coon) is able to control Cthulhu. After Cartman orders Cthulu to send Coon and Friends to a dark oblivion, Cthulhu is defeated by Mint-Berry Crunch (Coon vs. Coon and Friends), who had discovered his powers, and sent back to its world.

Powers
As shown when he attacks the Gulf of Mexico, Cthulu is truly a god, and is possibly the most powerful being in existence (although he is still defeated by Mint-Berry Crunch). His powers include:
 * Godlike Strength: Cthulu has enough strength to easily rip a massive Ferris wheel off of its hinges.
 * Lightning Touch: Cthulu can release lightning from his hands, which can completely incinerate a person.
 * Dimensional Travel: Cthulu has shown to be able to make an enemy be sent to R'lyeh by a wave of his hand.
 * Demon Command: As shown by the wave of creatures that attacked the Gulf of Mexico, these were probably his servents, meaning Cthulu has control over possibly trillions of demons, probably gained by his command of dimensions. The "demons" pouring across dimensions heavily resemble the "Elder Things" (also created by H.P. Lovecraft) from the Cthulhu Mythos universe, who work independently of Cthulhu, which may mean he is not in control after all. However, in the Cthulhu Mythos, he has command of a race called "The Star Spawn of Cthulhu" who, oddly enough, don't appear in South Park.
 * Immortality: In the original story "Call of Cthulhu" by H.P. Lovecraft, and "Trail of Cthulhu" by August Dereleth, Cthulhu would regenerate from any wound, up to and including a nuclear bomb. This is supported in the show when Kenny (as Mysterion) mentions Cthulhu being an immortal, and that only an immortal can kill another immortal.