Even if unbelief is dealt with at the cross, according to unlimited atonement, faith is still required for the application of the atonement that has been accomplished. In this case, there is no double-payment objection to answer, because those who are damned have simply not exercised the faith requisite for redemption. Christ dies for their sin, all right–including their unbelief; but if they do not have the faith necessary to have the benefits of his death applied to them, then they suffer the just punishment for their sin regardless. Oliver Crisp, Deviant Calvinism (230).
So Christ died to redeem unbelievers, who will still be damned because they are unbelievers! That's really ironic. Critics of 5-point Calvinism think it's a travesty of justice. Yet they resort to this Kafkaesque alternative. A divine Catch-22, as if God takes malicious delight in trapping them in this circular predicament.