Last paragraph got updated, it said something like “A cold hand touched my shoulder and the world started to spin”, which I interpreted as going to hell.

Last words could still be taunting for sure! I guess it depends on the tone you give to it. Either way, since Brad died, both contracts were fulfilled and payment is due.

I'm piggybacking off two comments here and adding my own thoughts so I can explain what I understood in full:

- OP's deal stood as long as Brad lived, and Brad's risk of dying was low because he was supposed to be bedridden forever, so OP should've lived a full life without consequences.

- Once Brad wasn't bedridden anymore (in exchange for her mom's soul), he tried to get his revenge, but OP killed him. So now that Brad is dead, OP's deal is done. Brad wasn't supposed to die so soon. Assuming that both brothers promised their respective souls as payment upon Brad's death, now they both gotta pay.

I think the final paragraph is key: I first read the "Hey bro. Have you seen mom?" as Brad taunting OP (like "lol, did you see what I did"). But if you read it as a genuine question and you add the "cold hand clutched my shoulder", I think it's just Brad's soul not remembering what happened and touching OP's shoulder/soul before they both go to hell ("the world started to spin").