
The character of Hector Hammond is a crook who becomes exposed to cosmic radiation from a meteor and develops mental powers. Hammond's beef with the space cop Green Lantern/Hal Jordan is, of course, over a girl.
Although Sinestro seems like a better choice for a villain, Sarsgaard is a compelling actor who can nicely pull off intelligent, slow-burn evil as well as wackadoo nutty. I mean, just look at the expression of pure malevolence in this photo taken from WireImage.
Also, after the jump, take a look at this cool fan-made trailer for a "What if?" Green Lantern movie starring Captain Hammer himself, Nathan Fillion.