I'm not surprised there is a way for werewolf to become an Alpha without killing one to take the power. I am surprised that its so rare that it only happens about hundred years. I was sure Derek's sister Laura became an Alpha without killing (since the Hale pack was killed off). Now I wonder how she became one then. This storyline is surprising and actually fitting when you look back on season 2 and we see Scott becoming more of a leader and rallying people behind him.
Now we at least understand why Deucalion wants to kill Scott or get Derek to do it. If Scott was just some regular Alpha I doubt he would care. I've been wondering what makes him so special. True Alpha is so special I'm willing to bet its more powerful than the Alphas who steal the power. Since Scott still hasn't fully become a True Alpha yet that his awakening is still far off and Deucalion is going to do whatever he can to stop it or get him to join.