This is the post I mentioned in an earlier blog.
Richard III is one of Shakespeare's greatest villains. He's willy and Machiavellian and at the end of the play (this doesn't ruin anything) he gets this just desert. The Joker, in The Dark Knight in particularly, also has incredible intellect and a taste for chaos.
Both of them also try to seduce a former enemy to work with them, though inside they know that the person they are manipulating is just a pawn in their plan. Richard seduces Lady Anne, whose husband Edward was slain by Richard just days(?) before the play stars. The Joker seduces Harvey Dent, whose wife was killed by the Joker just days earlier.
Richard's seduction of Anne is poetic and ironic. The language is colorful and it plays out so well you almost believe it could have happen (and it sort of did, historically). The Joker's discussion (page 106) of chance and fate with Harvey, on the other hand, is cringe inducing. You can't believe that Harvey, who seemed so reasonable and still does, would decide on a whim to leave the Joker's fate to chance. He has a gun to the head of the man who killed his wife and he doesn't pull the trigger.
If I could change one thing about The Dark Knight, it would be that scene.