Squeeks1337 says:
So it might be best to refer to it simply as Dark Side characters rather than 'evil' characters since in many ways the Dark Side is not inherently evil, at least from an outside perspective.
The dark side isn't the kind of evil that necessarily brings forth random psychosis and violence. It is, however, evil in a way, as intended by canon. It is part of the living force, and the dark part of it. It does the opposite of the light side, and pervades the individual, in a way corrupting them, taking them further along a path of... well, darkness. It's what allows the character to kill the younglings, force choke his true love, destroy a planet, etc. Anakin, the reference here, didn't intend to do any of those things. But a fork in the road started him down a dark path, and became so much a part of him, that it became who he was.
Another example is Count Dooku. In his case, he was less 'consumed' (I want to find another word, but am failing to do so) by the dark side, but was set on the path. He had strayed from the Jedi, and helped facilitate the political machinations that began the clone war. If his character lived longer, I am of the opinion he would evolved into a clearly darker character. At the same time, he considered himself to have seen the light by leaving the Jedi.
I think the simplest thing I could say about Vanguard of Darkness is that this game is about the villains, and how they come out on top. Assuming things go well for them.