TLDR: Shinra is Jesus EZ win
The only way to win now is to turn the cataclysm on its head. Notice how they keep repeating the conception that everything leads to death, but they feared Shinra cause he was the last world's interpretation of a savior (Jesus) which means he can do what Jesus did and show people Hope and how to keep on living. If people believe his teachings, the cataclysm would turn into a mechanism of death to one of life. They mentioned how the Evangelist spent millenia etching fear of death into the cultures of man which means she has no direct control. Of Shinra captures the heart of man he wins. The cataclysm only works off the imagination of people. Shinra shows life is worth living and the cataclysm will make a world where that is feasible.