'Nemesis' is actually the story of a super-villain (or at least someone who wears a crazy costume and kills a lot of people). DC Comics has a character with a similar name and the two should not be confused with each other.
In a sense, it's the opposite of 'Kick Ass' and asks what if supervillains existed in the real world rather than superheroes. In Millar's world, the superheroes have a much tougher time of things rather than in the standard Marvel or DC comics.
Millar's comics usually have over-the-top action, so Tony Scott is likely a good choice for directing a movie adaptation.