It has to be 'War is god.' That line cuts through the whole book like a rusty scalpel. It's not said by a character directly, but it's presented as this stark, terrible statement from the narrator about the judge's philosophy. It distills the novel's whole horrific worldview into three words. I read it and had to put the book down for a minute. Everything about the violence, the landscape, it all felt contained in that phrase. Not war as a tool or a tragedy, but as a divine, absolute force. The judge lives by it, and the book forces you to stare at it.
I've seen that quote pop up everywhere online, divorced from context, and it always gives me a chill. People use it to sound edgy sometimes, but in the novel, it's the bleakest possible truth. It's famous because it's unforgettable, and because it refuses any comforting interpretation. There's no room for 'war is hell' sentimentality there. It's just a cold, factual declaration about the nature of the world McCarthy built.