Dante would seem to be a key candidate for infernalism, the doctrine of endless punishment in hell for sinners who failed to turn to Christ.
He’s said to be medieval and isn't that what they believed then? And doesn’t his Divine Comedy clearly, indisputably say as much?
But Dante’s whole point is that nothing is as it seems to the unawakened eye.
I think what Dante is doing is taking evil completely seriously and showing why eternal damnation not only isn't, but can’t be the final result. And yet, this can only be seen when the darkness itself is fearlessly, fully seen.