Pure Evil

My view is that evil is unintentional. It is the misdirection of good intentions coupled with either ignorance, or a sense that ends justify the means (see Dr. Horrible for a good example). It is possible to have a stand-up hero become the antagonist quite inadvertently, and as such, is a recurring theme in comics (this theme is explored rather well in Alan Moore's Watchmen or even in something more contemporary like The Authority or even Red Son Superman). For the most part, contemporary literature/scripts have done away with the 2 dimensional evil persona (even Killer Robots now seem to have a deeper purpose for eradicating humankind).

However, where my definition fails, seems to be in the case of the truly arrogant. This is the person who is so self centered and ambitious that they do not care who is trampled underfoot (see Hamlet's uncle, or just about any history book for that matter). Is there something I am missing about this archetype that allows them to exist in such a flat manner? Or is there more depth than meets the eye?