Predators are always shown as sadistic. The first could've just killed Dutch at the end, but wanted to beat the living shit out of him with his bare hands. "Fair fight" my ass, he knew Dutch couldn't hurt him. The Elder Predator killing CH was because CH failed in his hunt, much the same way as them trying to blow themselves up when they lose.
All that being said, Kevin Peter Hall literally calls him a "bad blood" in a promo interview for the movie
I don't think he meant he was going against the Predator hunting code or whatever, just that he's a much more vicious, in-your-face killer. He's not the patient stalker from the first movie.