I didn't get the Villains section of the Role Archetypes thing done today, or even enough to post as a part, but I want to talk for a bit about what goes into the definition of a character as a Hero, or a Villain, or worse.
This moral scale deals with a somewhat complicated and nuanced notion of evil, which is hard to define, so instead I'll focus on the somewhat more simple notion of sin.
In a simple sense, sin is defined as failing to be good. While this definition at first seems to be no simpler than the matter of good and evil, it is worth noting that we don't necessarily need to consider the matter holistically when we engage a story.
In the psychological terms of analytical literary criticism, a hero in a story–strictly speaking an archetypal Hero, but the two are so closely related that there's not always a good reason to draw a distinction–represents an ideal for a society. This does not mean that they necessarily are perfect (look at Odysseus' boastfulness and occasional irreverence for the gods), but rather that they pursue improvement toward an ideal.
In this sense even a character who might seem morally reprehensible, like Deadpool, can be a character who is a heroic figure (technically, Deadpool fits the heroic bill quite well; he may "rebel" against being a good guy, but he is ultimately willing to make great sacrifices of himself).
In this sense, there's a scale of heroism that I want to present as a background before I discuss the matter of the villain, one which may help to explain what's going on with the characters.
A Model of Heroism versus Villainy
It's worth noting that I'm going to use Truth and Lie in a somewhat nonstandard sense here: Truth is the pursuit of moral goodness (however it is defined; stories' protagonists are not necessarily good by a universal moral standard), while a Lie is an effort to project goodness as the current state of a character who is not pursuing moral perfection. Jordan Peterson's Maps of Meaning (affiliate link) talks about this at length, though a simpler version is presented in his 12 Rules for Life.
... the central problem of life–the dealing with its brute facts–is not merely what and how to diminish suffering, but what and how to sacrifice to diminish suffering and evil–the conscious and voluntary and vengeful source of the worst suffering.
Jordan Peterson, Twelve Rules for Life: An Antidote to Chaos
In this sense the Lie that impedes a character's moral development may be expressed or hidden, an overt act of defiance and self-deification (as in Milton's Lucifer) or an act of self-deception (as in Victor Hugo's Inspector Jalvert). A character need not be clearly identifiable as evil to sin; Marcus Brutus in Shakespeare's Julius Caesar brings a special kind of hell to the world through nothing but the best of intentions carried out in ignorance.
Hero
Interested in being good, able to accept the changes that the Truth presents.
The Hero is a character that represents a fully-functional individual; they reconcile tradition and the need for change to break beyond their society's boundaries, but not transgress the moral Truth that they seek. They respond appropriately to what they learn about the world, and actively reject any Lie they encounter.
An example of this is unnecessary, as the Hero is nearly universal as the protagonist of stories with happy endings.
Tragic Hero
Interested in being good, but not able to meet the requirements of reality.
The Tragic Hero is a character that represents an individual in stasis; they embrace tradition but not the need for change. They are familiar with part of the Truth, but a Lie cracks their better judgment.
A good example of the tragic hero can be found in the form of Chinua Achebe's Okonkwo, from Things Fall Apart (one of my favorite novels, if not my favorite), whose adherence to a sort of hyper-tradition causes him to destroy everything he holds dear.
Anti-Hero
Morally apathetic, incapable of growing toward Truth.
The anti-hero is often a protagonist, or at least a protagonist-esque figure, but they embrace neither tradition nor change. They do not wholeheartedly embrace a Lie, but they never have a basis of Truth from which to operate.
The anti-hero is perhaps most well summed up by Kafka's Gregor Samsa, who is incapable of confronting the change inherent in life; not strengthened by any tradition (other than a fear of social pressures) and not willing to accept a path to strengthening himself.
Villain
Morally apathetic, willing to do evil and embrace a Lie.
The villain is often a sympathetic figure, because they represent the aftermath of tragedy. The villain has been deluded into a Lie by the Serpent, and if they ever knew Truth they reject it. They may become over-embedded in tradition (though a delusional view of reality can also underpin a villain), but in any case by self-deception they willingly pursue a Lie, though they would not necessarily accept the notion of creating destruction.
The villain, like the Hero, is well-represented in fiction to the point that naming an example is perhaps pointless, but Darth Vader in Star Wars is a good example of what a villain can do.
Serpent
Actively pursues a Lie and encourages others to do so.
The Serpent is the creator and greatest adherent of a Lie, a particular view that flies in the face of what they have experienced. This is the ultimate antithesis of seeking to do good, often merely couched in a notion of apathy or a rejection of morality as a meaningful conclusion.
A great example of this could be Milton's Lucifer or Tolkien's Melkor, who are aware of the presence of God but reject the divine plan in favor of what they desire; they delude themselves into a megalomania that drives them to reject all Truth in favor of their own Lie.
Wrapping Up
I think that this scale might help to make clear what I'm talking about when I refer to a Hero and a Serpent, and all the various steps in-between.
In any case, I'm now stuck listening to Philip Glass's "Metamorphosis", since I tend to do that.