“It's rare, it's something that doesn't happen within 100 years, but every once in a while, a beta can become an alpha without having to steal or take that power. They call it a true alpha. It's one who rises purely on the strength of the character, by virtue, by sheer force of will.” — Alan Deaton to Scott in Currents 3x07
Scott survives his "sacrifice" and fights Jennifer Blake alongside Deucalion. He refuses to kill her and becomes a True Alpha while pushing through a Mountain Ash barrier.
Derek sacrifices himself for his friends, his family, his pack.
Basically all I’m saying is that Derek became a true alpha in his final moments, I don’t care what anybody says.
Yes I know it’s a rare occurrence, but even though Derek has killed for love and for revenge he died protecting those he loves and cares for.
Now that I'm thinking about it, it makes sense why Stiles isn't in the movie because the dude would've turned that 2-hour long movie into an hour and here's why.
• If he was at the scene of the fires he would've figured out that burning these trees would make mountain ash.
•Once Liam told them that it was the Nogitsune and it was released by someone with a vendetta against them he would've started compiling a suspect list(including people that are dead cause this Beacon Hills)
•Not letting Derek kill himself and essentially making the sacrifice play himself
Also, let's not even mention the fact that he and Eli would-be sarcastic little shits the entire time.