There’s reasonable evidence that an afterlife exists. There’s also good reasons to think that God exists.
Now if an afterlife exists and God exists, then what would such an afterlife look like?
Well I don’t think God by nature would be justified in allowing the afterlife to not be good. After-all, the afterlife does seem to go on forever. An afterlife created by God that’s not good, seems to cast doubt on God’s mercy,patience, and love. Similarly, if God had no punishment for sinners who reject Christ, that would cast doubt on God’s justice.
Well why think that? Well the evidence that we have for the afterlife is such that the nature is fundamentally immaterial. People have experiences that are seemingly out of their physical bodies.
A lot of these experiences are not just boring nor nightmarish. Rather, these experiences are described as blissful, peaceful, and fulfilling.