Are there possible worlds that include unimaginable suffering? On behalf of the Anselmian theist, Tom Morris denies that there are such worlds.
Such an [Anselmian] God is a delimiter of possibilities. If there is a being who exists necessarily, and is necessarily omnipotent, omniscient, and good, then many states of affairs which otherwise would represent genuine possibilities, and which by all non-theistic tests of logic and semantics do represent genuine possibilities, are strictly impossible in the strongest sense. In particular, worlds containing certain sorts or amounts of disvalue or evil are metaphysically ruled out by the nature of God, divinely precluded from the realm of real possibility. (‘The Necessity of God’s Goodness’ in his Anselmian Explorations 48 ff.)
But I think there’s an interesting argument that there are such worlds. I call it the Property Argument.