Abaddon, a Knight of Hell, took down the unique Males of Letters … single-handedly. She’s the worst sort of villain, from the Winchesters’ perspective: massively highly effective, and completely determined for management. Educated by the biblical Cain, Abaddon is an historical menace, well-accustomed to blood and mayhem. There is no such thing as a one she won’t possess, slaughter, or maim to get what she desires.
After time-traveling to the current day, she decides to pursue her greatest plan but: develop into the Queen of Hell and rule demons, people, and angels. Like so many baddies, she desires to rule the world by means of huge armies, reserves of energy, and iron legislation. Too unhealthy she comes throughout Sam and Dean Winchester.
Dean, empowered by the Mark of Cain, ultimately kills Abaddon with the First Blade, a relic as soon as described as “probably the most harmful weapon on the planet.” Thus falls Abaddon: Knight of Hell, historical evil, aspirant Queen of Hell.