Contradictions
The Quran claims that no soul will bear the burden of anothers:
Quran 35:18
No soul burdened with sin will bear the burden of another. And if a sin-burdened soul cries for help with its burden, none of it will be carried—even by a close relative. You ˹O Prophet˺ can only warn those who stand in awe of their Lord without seeing Him1 and establish prayer. Whoever purifies themselves, they only do so for their own good. And to Allah is the final return.
And then later claims that they will bear the burdens of others:
Quran 16:25
Let them bear their burdens in full on the Day of Judgment as well as some of the burdens of those they mislead without knowledge. Evil indeed is what they will bear!
Them bearing the burdens of others is also repeated elsewhere in the Quran:
Quran 29:13
Yet they will certainly ˹be made to˺ carry their own burdens, as well as other burdens along with their own. And they will surely be questioned on Judgment Day about what they used to fabricate.
The Quran contradicts itself completely. If we look at the Hadiths, we can see that it agrees with the earlier Quran surahs, where both the Christians and Jews will be used to save Muslims from hellfire:
Sahih Muslim Book 37, Hadith Number 6668
Abu Burda reported Allah's Messenger (may peace be upon him) as saying: There would come people amongst the Muslims on the Day of Resurrection with as heavy sins as a mountain, and Allah would forgive them and He would place in their stead the Jews and the Christians. (As far as I think), Abu Raub said: I do not know as to who is in doubt. Abu Burda said: I narrated it to 'Umar b. 'Abd al-'Aziz, whereupon he said: Was it your father who narrated it to you from Allah's Apostle (may peace be upon him)? I said: Yes.
Allah specifically tells us that if there are inconsistencies in the Quran, then it is not from Allah:
Quran 4:82
Do they not then reflect on the Quran? Had it been from anyone other than Allah, they would have certainly found in it many inconsistencies.
Reflecting on the Quran, we have found many inconsistencies. While this site details one, if you are curious about more contradictions, there are dozens detailed at The WikiIslam.
A Christians View
While the Quran is confused on how judgement is handled, Christianity is explicitly clear. Every single person is responsible for their own sin, but there is a beautiful solution to this: Jesus, being perfect and sinless, voluntarily took the burden of ours sins upon himself on the cross.
1 Peter 2:24
He himself bore our sins in his body on the tree
It's not an injustice or a contradiction; it is an act of perfect love. God remains perfectly just by still punishing sin, but also perfectly merciful by offering forgiveness to those who accept Jesus's sacrifice. He bore the burden of our sins so that we would not have to.