Kill the demon.

Ah, the basic assumption is that the devil is a liar, so, why would anyone "sign" anything with a liar ?

The devil got his soul just by signing the "pact"

I suppose, this is natural selection and supernatural level

Yes, yes, I know that all could be just fake and so on, but, it could also be true

Aftherlife cannot be proven to exist or not to exist, it is a bet, that may be won or not

Parkland shooter pulled the same shitty scam, convinced no one