Wa alaikum assalam
The simple answer is fairly. The Quran repeatedly underscores the maxim that God is most just and that not an iota of injustice will take place (4:40) as our Lord is perfect as judge. This is also supported by the following verses:
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"This is because your Lord does not destroy the townships arbitrarily while their people are unconscious / unaware (of the wrong they do)."
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"And for all there will be ranks / degrees from what they did. And your Lord is not unaware of what they do."
As to the details of exactly how they will be judged, this information was not even given to Prophet Moses, as a similar question as to yours was also asked by Pharaoh.
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"He (Pharaoh) said: "What then is the case of the former generations?""
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"He (Moses) said: "Its knowledge is with my Lord in a Record. My Lord neither errs nor forgets"
Hence, with all humility and respect, I would dare not attempt to answer a question that even Prophet Moses did not answer and I would rather repeat with humility that, "Its knowledge is with my Lord in a Record. My Lord neither errs nor forgets".
I hope that helps, God willing
Joseph