
Were we watching the same Movie? Ok, first, it's been stated several time by Anderson and crew that all Predators were young and had to earn their clan mark. As seen in the movie, if the last Pred would've been already an experienced veteran then why the heck would he need a mark? Secondly, he was just as much armored as the other 2 Predators. Did you maybe take your glasses off midway through the movie?
The only thing the movie showed is that even among Predators there are cocky teenagers. Like the first two that were killed clearly showed. The 3rd Predator was the kind that paid better attention during class and wasn't as impatient as the others.
You're actually the very first person that I've ever seen that actually has the whacky idea that Scar was a Veteran.