What would have been the first thing Peter would have done after he killed Scott and became an Alpha? Kill Stiles? No, I don’t think that would have been too hurtful. I think Peter would have bitten Stiles. Make him a werewolf. Make him stronger, make him follow his Alpha. Make him live a life without Scott in it. He would have forced Stiles to follow him, away from the Sheriff. And with Stiles, along would have come Derek. And Malia. And Lydia. What more could Peter have needed?