Buffy/Cas
Oh, wow. Yeah, no no. Not like that at all. She just kind of.. got consumed by her own magic. I don't really know how to explain it, this isn't my thing. But, she took a lot of dark magic out of books. Like literally. That was just the icing on her crazy evil cake though.
Look, even if you do manage to bind her, it won't last. Her magic is crazy strong, like.. world ending strong. We didn't stop her with magic before. And.. the person who actually got her to go back to normal isn't here.