Peter Pettigrew: Harry your parents wouldn't want me to be killed!
Harry (on his mind): nah I'll just let him be killed. He deserves it. Besides if I let him live he'll probably help Voldemort come back
Lupin: You should've known Peter if Voldemort didn't kill you we would!
Sirius and Lupin throw avada kedavra at Peter Pettigrew and Peter Pettigrew dies
Sirius: woohoo! It took me 12 years but I finally got my revenge!
The end