The Ultimate "Yes Man"
As a captain of the guards, your job is pretty clear-cut. If the warden says, "Jump," you ask, "How high?" If he says to put on a wig, sing "Take Me Out to the Ballgame" and dance the Macarena, you ask, "What key do you want that song in?"
For all intents and purposes, Captain Hadley should really terrify us more than the warden does. He's big and burly, with a steely-eyed glare. He beats one inmate literally to death, and at another time nearly throws Andy over the side of a building. Not to mention his cold-hearted execution of Tommy, who didn't do a single thing wrong other than unintentionally throw a snag into the warden's criminal activity.
However, while we don't necessarily want to share a booth at Denny's with the guy, he's not nearly as terrifying as Norton. Reason being that he's just a tool. The warden picks him up and fires him at the inmates as if he were waving around a loaded weapon. Yeah, he does some pretty awful things, but at the end of the day, he's just doing his job. He's not capable of acting independently.