Looking for a book with a “village crazy Lady is actually a badass” twist

Hey guys! As i said in the title, i'd like a book where the "village crazy lady" or a character who goes around spreading random wisdom and handing out cookies (eg) turns out to be a total baddie. Like some monsters show up and they just casually obliterate them and leave everyone with their mouths hanging open. Like, do you know the video from that gym where one guy has a shirt saying "i'm nice because i'm savage af"? That vibe!
Thank your for All recommendations!!