They are the reason we are not ruling the world!
~ Zeus

Zeus, the King of the Greek Gods, was the main antagonist in the season 7 episode Remember the Titans of Supernatural.

Zeus used to rule the Earth in the distant past, before the Abrahamic religion came along, and before God established himself as the strongest deity. Zeus was one of the most powerful of all the gods seen so far. He was a firm commander, ruling in a military-style fashion; and inspiring fear and envy through his kingdom on Mount Olympus.

However, at the same time, Eve appeared on Earth and threatened humanity by making an army of monsters. Knowing humanity would soon be slaughtered the Titan Prometheus decided to rebel against Zeus and steal Fire for humanity to fight back against the dark magic of Eve. This was successful, and it advanced humanity a long way, but Zeus cursed Prometheus and his offspring. Zeus in response cursed Prometheus to die every single day, and chained him to a mountain in Europe forever. However, many centuries later in the 1980s, a mountain climber named Hayley came up the mountain and an avalanche accidentally freed Prometheus. Hayley found Prometheus in the wreckage of the avalanche, with no signs of his divinity, and complete memory loss. He now decided to call himself "Shane" and live with her as a human.

Soon, though, Prometheus learned Zeus' true sadistic nature: His curse meant Prometheus would die tragically (and violently) at the end of each day. Prometheus was walking home one night, when a van hit him. Prometheus only stood there watching, knowing his fate by now, this being one of many times it had happened. He was smashed apart and thrown on the side of the road. A police officer soon found his corpse, later that morning, and called paramedics. An eagle happened to land on "Shane's" corpse and peck his liver out. However, the eagle then flew off. Moments later, unseen by the officer, Prometheus healed completely, and he stood wearily up and began to walk off back home. The officer heard a noise, and, turning, found no corpse. Fearing a theft, he followed footsteps to the woods, but found no one. Now scared and confused, he decided it was probably a zombie, half-jokingly, and called the papers.

This "zombie" account attracted the Winchesters who looked into the lore on the subject, tracked Prometheus down, and actually met him. However, unlike the other gods they had met, Prometheus was kind, intelligent, witty, remorseful and patient, understanding and liking humans because he sacrificed his life to save them. So, the Winchesters grew to like him, the only god they'd befriended (though they did not realize he was a god at the time, nor did he as he was suffering from Amnesia).
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Zeus displaying lightning bolts in a display very similar to Palpatine

One night however Zeus daughter Artemis arrived for Prometheus upon her fathers orders. Stirred by the danger Prometheus recovered his other powers and managed to fight her off, Artemis was forced to retreat. Using the dagger she left and the evidence they had, they realized who Prometheus really was. However at that point his former lover Hayley, who had accidently freed him from the mountain (by causing a landslide that also caused him to loose his memories) arrived and revealed he'd sired a son, Oliver, who had inherited his curse.

Knowing only Zeus could lift it, the brothers did some research and found an ancient Greek hunter had tangled with Zeus many thousands of years earlier and had discovered his weakness, a stake made of a tree struck by lightning. Summoning Zeus they trapped him in a special sign demanding he lift the curse.
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Zeus' Evil Grin

Zeus appeared and initially he was very charming and persuasive. However he refused to lift the curse unless he was freed, not trusting him the others did not. However Haley desperate for her son made the mistake of doing so. Once free Zeus turned his godlike power against them and defeated them. He then laughed at the idea of lifting Oliver's curse, finding the idea of being able to torture father and son for eternity to be amusing.

The Brothers tried to fight back, but Artemis arrived and over powered Them. As such Zeus carried on torturing Prometheus. However Sam managed to figure out that Artemis had secretly fallen for Prometheus hence why it had taken six years for her to track him down. He convinced her to turn on her father.

Artemis tried to intervene armed with her bow, Zeus tried reason with his daughter, but refused to stop. Artemis tried to shoot him, but Zeus grabbed Prometheus and used him as a shield, however before the arrow killed him, a furious Prometheus pushed the arrow through himself into Zeus taking the king of the gods with him. This broke the curse, freeing Oliver and allowed Prometheus a final death.