I was chatting with my Shakespeare class about new media trying to humanize evil (NCOM, TWBB, Margot At The Wedding) and we decided that the NCOM has (Aside from Ed Tom Bell) mostly flat characters. Josh Brolin is evil because his actions are all governed by greed, and Chiguhr is evil because he has no regard for human life. Hence the coins: He doesn't even care if they live or die, you decide heads or tails. Means nothing too him, but there's something about it he enjoys. Anyway, Plainview is a different story altogether. It's unclear what governs his evil (much like Iago), but there's certainly more to him than greed or apathy. A case could be made for wrath, I'd say... never sloth, or envy, maybe gluttony... but certainly the character has extreme depth and as a villain, that makes him more evil than anyone in NCOM.

he realises his "brother" is a fake. You can see the bottom drop out of Plainview's stomach, see his heart break, see him almost lose it.

his character is feeling overwhelmed by this new breed of evil and he goes to his uncle who tells him that feeling overwhelmed is vanity, that evil doesn't change, and that you do not live in the center of the universe. No matter how overwhelmed you feel, it's still not about you. It's the same old deal. Tommy Lee Jones read the book, and says it's very important that people see this movie or read the book or something. Here, I'll type out his quote about the final scene. Seriously this is extreme spoilers, don't read ahead if you haven't seen the movie (for your sake).
Tommy Lee Jones: "Like all considerations of Cormac, the questions are more important than the answers. The question that arises there [in the final scene] is that wonderful dream of riding ahead and reuniting with your father in the warm fireplace in the cold, in the dark hostile country. And if it is a dream, does the dream have any efficacy at all? If you wake up from a dream, have you woken up from reality? So these get to be pretty sophisticated questions and I really appreciate the Coen Brothers' careful reading of Cormac's moral thinking. Finally we're left with really good questions which are better than simple answers."
It's pretty weighty topic for discussion, but I just have to say I think TWBB's two main characters are more evil than Chigurh or Brolin's character (who I read more like Camus's "The Outsider" than as a manifestation of evil or greed), but what makes No Country For Old Men so great is that third character that just doesn't exist in TWBB. He represents justice and morality in the face of horrible, horrible evil, and how can we as just, moral beings exist in a place where there is just seemingly no place for Justice or Morality? Hence the title.