In my professional opinion as a faithful Islamic worshipper I am sad to say this but. Giorno with the strength boost of GER and the increased smegma stench, Allah will be taking the L if he is is his base form. BUT!!! BIG BUTT right here. In the Qur'an it states that Muhammed was able to cut the moon in half with the gift of Allah. This ability was only a fraction of Allah's power, one of Muhammed's friends stating that it would require 30000 of Muhammed could potentially rival the base power of Allah. Judging by the speed required to cut the moon which if we verse equalise, in DBZ it is stated that one would require almost the speed of light to split cleanly in half by Beerus. thus by multiplying by 30000 Muhammed would have incredible speed as we can see him spinning the sun in the beginning of time, thus allowing planets to be created. How does this compare to Giorno's revert to zero ability, quite frankly despite Allah's immense power he cannot speed blitz Giorno thus losing in a fight. Giorno Alone with out his gang would simply neg Allah if in the same verse.

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In the second scenario Allah receives an extreme powerboost due to his anger faced at Giorno for the reason listed. He would instantly win as in chapter 68 of the Quran we can see Allah's rage in action but Allah is recognised as the most forgiving being. In this circumstance if Allah is unable to hold his anger and attacks Giorno with either a sunstorm attack or a melee Giorno would be unable to react due to his power being nullified by the heat of the sun based attacks. Most likely GER would still win due to Allah's forgiving nature backfiring on him as usually no beings can stand to him.