There is a way they can bring Superior back. Suppose he Otto didn't delete himself at the end of the first Superior run. Instead, he only appeared to delete himself, but instead, transferred his consciousness elsewhere, similar to how he survived at the end of Spider-verse. So now he's been biding his time while volume 2 Superior is having his adventures, maybe curious to see how this version of him turns out. After volume 2 Superior makes his deal with Mephisto, volume 1 Superior decides to come back feeling that his other self has wasted the chance he was given, and needs to make things right again,