Sinestro
From a young age, Sinestro understood fear. In towering over friends and banishing the lizards to their holes, he saw it in their eyes.
Fear of him.
It gave him power. It made the universe understandable. Fear was what pushed things to be better, much more than they used to be. When he became a Green Lantern, he tried to apply this philosophy to his work.
The Guardians promptly kicked him out.
That was a good thing, though, as like-minded individuals joined him with birthing fear into tangible might.
Soon, millions experienced fear at the Sinestro Corps' hands.
He loved it.