The justice of the reprobates' eternal punishment in hell
Hell does not necessarily impose an infinite punishment, and the sins of the reprobate are not necessarily finite. Biblical Christianity is perfectly flexible on both of these points. Either one of them, in isolation, is enough to fully answer the objection of "infinitely disproportionate punishment", and we have both. So we can say with confidence that the reprobate in hell will get exactly what they deserve - the exact right level of punishment commensurate with their sins.