If Chigurh is a bad guy, and Llewelyn Moss is a neutral guy, then Sheriff Bell is the good guy of the story by default.
And he's completely useless.
Yep, No Country for Old Men is a battle between good and evil, except it's hardly a battle, because Bell and Chigurh never confront each other, and evil most definitely wins. Imagine if David fought Goliath, but David never actually showed up, and Goliath took the opportunity to stomp out a few villages. Yeah, Sheriff Bell is our absent David.
Bell wants to protect Llewelyn. He fails. He wants to help Carla Jean. He fails. He doesn't capture Chigurh, who disappears at the end, presumably to continue killing and killing. Why even be in law enforcement if the drug trade keeps growing and growing and getting more violent and destructive?
Sheriff Bell knows the futility of fighting, and he suffers from it. The level of sheer evil Bell encounters escalates quickly in this book. The first time we see Bell, he's talking to a woman about getting a cat from a tree. Before we know it, he's trailing Chigurh, who leaves numerous bloody bodies in his wake.
What's the point of it all? All Bell seems to be doing is delaying the inevitable fall of society, and he's not even delaying it by all that much. "Sometimes things turns out all right" (5.2.132), he says. But this time, things don't turn out all right.
Bell may be a failure as an officer, but at least he has his coffee. In fact, he drinks so much coffee, we're surprised this book is set in Texas and not Twin Peaks.
He also has his wife, Loretta, whom he married when she was 18. He loves her, and he believes that he wouldn't be able to do his job without her. I dont believe you could do this job without a wife (6.1.3). See? He thinks it in almost exactly those words.
However, Bell's job is so emasculating that he starts questioning his own manhood. He knows that "the only reason I'm even still alive is that they have no respect for me"(8.1.2). And that's true. Even Wells thinks Bell is a "redneck sheriff in a hick town in a hick county" (5.3.293).
If Chigurh thought Bell was a threat, he would have killed him. That's a humiliating thought.
So all Bell has left is his lovely wife. "She's a better person than me, which I will admit to anybody that cares to listen. […] She's a better person than anybody I know. Period" (4.1.1). This might sound a bit like the rambling of an old fuddy-duddy, but hold up. Love and a good marriage may not seem like all that much in the grand scheme of the book, but actually, this is our one ray of light. These are actually good people, people who don't give in to temptations of evil.
In this book, evil may be stronger than good, but it's the good people who actually achieve some kind of happiness, even in the midst of all that evil. And that's something.
On a final note, Bell does feels guilty about something. When he was in the war, he got a medal. But he only got a medal because he survived… and all his friends died. He's always carried a feeling of guilt about this, until he finally decides to tell his wife his secret to absolve himself.
Do we care? We're not sure. Bell's guilt seems so insignificant in the grand scheme of things. Does he feel the same sort of guilt over letting Llewelyn die while he himself lives to fight—and fail—again another day? Probably. And that, too, is something.