If you are truly badass, you are an individual compentent on the scale you see in a movie. You're able to fight well, sneak around quietly, and be generally impressive. You are the one crawling out of the car wreck after the explosion. You are the secret agent that can impress the ladies, fight off all of the guards, and even engage in witty banter while in a deadly situation.

Such a level of competence implies lessers; since this idea itself comes from the entertainment industry, I'll call them extras; you can think of them as red shirts, scrubs, or mooks. These extras have no real identity and are not worthy foes, and can be easily dispatched.

How to tell if someone is truly badass, at least in the cinematic sense:

  • They scare extras without trying, and can kill them without having to work at it.
  • They can recognize things easily -- they identify fighter aircraft by the engine noise, for instance.
  • They appear out of nowhere and disappear equally well.
  • When they want to be conspicuous, everyone will notice them, growing silent when they enter the room.
  • Their equipment doesn't break down.
  • When they play against mooks, they win.
Note that the Space Marines in Aliens claimed to be ultimate badasses, but unfortunately were not. On the other hand, Raven from Snow Crash is decidedly truly badass, though since it's a book it works somewhat differently.

Also, an advantage for cinematic roleplaying for GURPS created by S. John Ross.