The Godslayer

An enemy of the world, and possibly the best gunslinger Eos has ever had, he single-handedly terrorized the entire world for decades until he was put down by Chaos. Ages later, his influence still remains in this world.

Backstory
Born Eonian prince, he quickly ascended to the throne at the proud age of 14, after his father was meritoriously assassinated in his very room. He quickly lead an advance in Eonian society, so much so that it is said the technology made under his rule wasn't far behind that of Owari's civilization.

Several years after, he declared a surprise war to the twelfth's world, and he effectively eradicated every single lifeform in the planet before killing the deity himself.

Chaos, of course, was furious after he found out, and he immediately asked he be executed on the spot, to which all the other deities complied. His "corpse" was buried in one of Eos's moons.

Several years later, Chaos flew to the moon in question in search for his corpse, finding that he had never been buried, destroying the moon in a fit of rage.

In the following years, the Godslayer somehow managed to instigate a second war against the eleventh and possibly the downfall of Owari's civilization, he is also known for trying to kill Bao's Host, several times.

He is attributed at least a third to half of all the deaths in both galactic wars, and a quarter of the deaths in the downfall, having effectively killed billions by himself.

He was finally shot down by Chaos at the age of 47.