Why does everybody seem to think that negative traits and/or unlikeability = poor character? Stories would be boring if everybody was a likeable, honest character.
Like Roy Earle, for example. He has a strong character and provides an important role in the game. Yet, because he doesn't act in the best interests of the player, he's suddenly worst character ever? That just plain doesn't make any sense.
The same goes for characters like Miranda and Brucie that I also saw mentioned as well. The worst character ever is a title that has to go to somebody so utterly bland, one-note and incapable of progression that there is absolutely no value to having them in a story.
I nominate Harbinger.