You know, you cannot defeat XE037.
A perfect analogy would be to have the U.S. declare war on fish. Sure they could attack the ocean ocean with everything, but there are just too many fish inside it to successfully kill them all. Well I guess you could nuke the Earth to smithereens and have fallout kill the fish, but that would also kill everything else.
So successfully defeating XE037 is not a possible thing, because it’s everywhere (you, zombies, insects, every single animal, perhaps even in plants), theres no centralized being you could successfully defeat to get rid of the XE 037. Short of leaving Earth and make a safe colony with only clean organisms, the cataclysm is unfixable.
Even leaving Earth couldn’t ensure your escape if the dimensional degeneration will expand through the universe without limits (Why would you even care anyways, Cataclysm is not a game about escaping to space and founding a colony or something).