au: lydia kills peter.

"I used powder of wolfsbane from Deaton’s spice cabinet to subdue him.  He wasn’t quite unconscious after that, said something about how I couldn’t go through with it, that we had unfinished business to attend to.  He got to watch as I drove the knife into his chest.  I buried the body at the ice rink—Boyd didn’t exactly say that it was okay, but he did leave me the keys to the zamboni, and, well, I think that’s permission enough, don’t you?”

"Are you telling me that you killed an alpha werewolf?  That you killed Peter Hale?"

Lydia smiles.  ”What, like it’s hard?”