According to a blog post This is what another universe looks like, "in Arthur Schopenhauer's 1844 work "Von der Nichtigkeit und dem Leiden des Lebens", he argues that our world must be the worst of all possible worlds, because if it were significantly worse in any respect it could not continue to exist".
But if we live in the worst possible world, then better worlds are able to continue to exist which means worse worlds than possibly-existing worlds can exist which means worse worlds than currently-existing worlds can exist.
Which argument is wrong?