He's always casted away by society, and tries to solve it with violence.
Man on Fire
Training Day...just two of the top of my head...but there's more. Im not saying it's a bad thing. Some actors are better that way.
A flamethrower, customizable cars(in depth),...and DLC that takes you outside of the original map. I was disappointed that GTA IV didn't expand liberty city. A trip back to Niko's Homeland would have been awesome.