Will power. In DC Comics, Hal Jordan and his comrades in the Green Lantern Corps focus it through a ring that can make or do nearly anything. Green Lantern stories imply that Green Lanterns have more, purer, and stronger will power than anyone.
Too bad that’s not true.
When we call people strong-willed, we mean that they obey no one’s will but their own. The most famous film about Adolf Hitler is titled Triumph of the Will, hinting that Hitler rose to conquer Germany by applying tenacity and determination; and the movie got that part right. In The Godfather, Mario Puzo described mafia bosses as men whose will was so strong that they refused to knuckle under to any authority, even the cops and the courts. A person with more will than anyone else — that is, more drive, desire, and ambition — isn’t going to take orders.
But the Green Lanterns have usually obeyed the orders of little blue men half a universe away, the self-appointed Guardians of the Universe.
If the Green Lanterns did have truly supreme will, then they wouldn’t work for the Guardians. Can you imagine Hitler or a mafia kingpin saying, “Yes, sir, right away, sir” if he didn’t have to?
When Green Lanterns do prove themselves supremely strong-willed, the Guardians don’t like it. All the way back in Green Lantern #7, by John Broome, Gil Kane, and Joe Giella, the Green Lantern Sinestro proved too willful for the Guardians to control. He says it himself: “I am Green Lantern — no one can tell me what to do!”
So the Guardians kicked him out of the Corps.
They’ve even punished Hal Jordan for being too willful. In Green Lantern #76, by Denny O’Neil, Neal Adams, and Frank Giacoia, an enraged Hal was about to slug a slumlord when the Guardians ordered him to leave, chewed him out, and told him to go away and cool off until they called him. When he defied them and returned to Earth — that is, when he asserted his own will — they got even madder.
You can do a lot of things in the Green Lantern Corps — but don’t demonstrate too much will.
(P.S. DC has shown at least one character with more will power than a Green Lantern. In Justice League International #18, by Keith Giffen, J.M DeMatteis, Kevin Maguire, and Al Gordon, the interstellar badass Lobo walked right through a barrier that the Green Lantern G’Nort constructed. G’Nort’s a comedy-relief character, so maybe he doesn’t represent the bulk of the Green Lantern Corps. But he’s still one of them.)