This is cut and pasted from this site, entire post highly recommended
The Villain We Love to Hate
Watching Shakespeare’s character lie, manipulate, and murder his way to the English throne is a lot like watching the Grinch steal Christmas or Sue Sylvester humiliate the Glee Club: we know we’re witnessing the actions of an unapologetic villain, but we just can’t help but be enthralled and even amused by it.
This is partly because he’s smart, suave, and politically savvy. He also has quite a sense of humor. It’s a sick sense of humor, sure, but it can be pretty compelling. (When the hired murderers promise to make Clarence suffer, Richard quips “I like you lads”.) More important, Richard also has a habit of confiding in his audience, making us his confidants. This has the effect of drawing us in and making us complicit in his evil schemes.
Richard and the “Vice” Figure Tradition
Richard is considered a throwback to the stock character of “Vice,” a common figure in medieval morality plays. The “Vice” character is basically a personification of evil and/or an agent of the devil who spends most of his time trying to corrupt mankind. Vice figures would often address the audience directly and would sometimes run around in the audience heckling people. This character can be a lot of fun but is also pretty one-dimensional. Vice doesn’t have any psychological motives – he’s just pure, concentrated evil, kind of like a Decepticon Transformer.
Obviously Shakespeare had all of this in mind when he created his villain. Richard is unapologetically wicked and is even accused of being an agent of the devil. … Richard even refers to himself as a “Vice” when he describes his actions:
Thus, like the formal Vice, Iniquity,
I moralize two meanings in one word.
Although Richard definitely has some roots in the Vice tradition, his character is a lot more complex than the flat, stock figure from the old morality plays. Whereas Vice figures have no psychological motives, we can argue that Richard does. In his opening speech, he tells us that he’s aware of his physical deformities and feels insecure, inadequate, and isolated. In other words, Richard’s got psychological depth from the very beginning of the play.
P.S. Shakespeare’s character Iago (Othello) also has some roots in the old Vice figure tradition.