10 Video Games Where You Work With The Villain
1. The Arbiter - Halo 3
While the first Halo wasn't bad by any stretch, it needed a little more character, something to add that vital bit of intrigue to make the story that much more compelling. Bungie's solution was The Arbiter, a proper rival for The Master Chief and an interesting look at the other side of the human/covenant argument.
His character would be properly fleshed out in shows like Halo Legends, and novels like Karen Traviss' Glasslands trilogy, but in 2, he was just an agent specifically assigned to hunting down The Master Chief to restore his honor in the eyes of the Covenant.
What he instead finds is that the Covenant really are just a bunch of psychopaths, and in 3, Arbiter and his people team up with the humans to take them down for good.
Add on top of all of this the brilliant voice of Keith David and you get by far the most compelling arc in the entire halo franchise, and the coolest instance of a villain and a hero teaming up to take down the greater threat.