The tension is understandable, but it rests on a false assumption: that the grave is the final verdict. In Islamic teaching, barzakh is a real intermediate state, while the Day of Judgment is the public, complete, embodied, and final settling of accounts.
Why the question feels strong
The objection can be put fairly like this: if a soul is already comforted or punished after death, then its case seems already decided. If the grave expands for one person and constricts for another, what is left for the Day of Judgment? And if someone punished in the grave later enters Paradise, was that earlier punishment only a provisional sentence?
That is a serious question because Islam does teach both realities: an intermediate life after death, and a final resurrection and judgment. The answer is not to deny either one, but to understand their different roles.
What the grave does - and does not decide
The Quran itself distinguishes between punishment before the Hour and the greater punishment after it. About Pharaoh's people, Allah says:
"The Fire, they are exposed to it morning and evening. And the Day the Hour appears: 'Admit the people of Pharaoh to the severest punishment.'"
Quran 40:46
This verse is central. There is exposure before the Hour, then a more severe punishment when the Hour comes. So the barzakh is not a rival Day of Judgment. It is the first stage of the next life.
The Prophet (PBUH) also taught that the dead are shown their destination:
"When one of you dies, his place is shown to him morning and evening. If he is among the people of Paradise, then among the people of Paradise; and if he is among the people of the Fire, then among the people of the Fire."
Sahih al-Bukhari and Sahih Muslim
This does not mean the final accounting has become unnecessary. Allah does not need a court date to learn the truth. The Day of Judgment is not for Allah to discover facts; it is for the whole creation to witness perfect justice, for records to be laid open, for bodies to be raised, for rights between creatures to be settled, for intercession and mercy to appear, and for the final eternal abode to be entered.
Why the Day of Judgment is not a formality
The grave can contain comfort or punishment, but it is not the full scale of judgment. Many matters remain: public vindication, the weighing of deeds, crossing the Sirat, repayment of wrongs done to others, degrees in Paradise, levels in punishment, and the final decree concerning those who died upon faith but carried sins.
The Quran repeatedly describes the Day as the time when deeds are fully displayed and no one is wronged:
"So whoever does an atom's weight of good will see it, and whoever does an atom's weight of evil will see it."
Quran 99:7-8
That is broader than the grave. Barzakh is like the dawn before sunrise: real light, but not the full day.
Can someone punished in the grave enter Paradise?
Yes, if he died upon faith and Allah forgives him, purifies him, or accepts intercession for him. Punishment in the grave does not necessarily mean eternal damnation. The Prophet (PBUH) passed by two graves and said their occupants were being punished for sins, one connected to carelessness regarding urine and the other to tale-bearing, as reported in Sahih al-Bukhari and Sahih Muslim. These were punishments for real sins, not a final declaration that repentance, forgiveness, or eventual salvation is impossible for every sinner.
The Quran gives the governing principle:
"Indeed, Allah does not forgive association with Him, but He forgives what is less than that for whom He wills."
Quran 4:48
So the doctrine establishes this: death is not unconscious nothingness; the soul enters a real intermediate state, with blessing or distress according to Allah's justice. It does not establish that the Day of Judgment is redundant, nor that every punishment before it is eternal.
The Islamic picture is layered, not contradictory: barzakh begins the encounter with one's deeds; the Day of Judgment completes it openly, perfectly, and forever.