Why does Allah punish with the fire?

How would you feel about someone who dissociated himself from his parents, kicked them out of the house, and left them in the street?

If someone said that he would let this person in his house, treat him with generosity, feed him, and thank him for such an act, would people appreciate that for him? Would people accept that from him? Bearing in mind that Allah has the highest attributes, what destiny do we expect for someone who rejected his Creator and disbelieved in Him? Whoever is punished with fire is as if put in his due place, as he despised peace and goodness on earth, thus, became unworthy of the bliss of Paradise.

What destiny do we expect for someone who tortures children with chemical weapons? Do we expect him to enter Paradise without reckoning?!

Their sin is not limited to a certain time; rather, it is a consistent trait.

{...And even if they were sent back, they would surely return to what they were forbidden, for they are indeed liars.} [309] Surat al-An‘ām: 28.

They even swear false oath in the presence of Allah on the Day of Judgment.

{On the Day when Allah will raise them all, they will swear to Him as they swear to you, thinking that they have something to stand on. Indeed, it is they who are the liars.} [310] Surat al-Mujādilah: 18.

Moreover, evil can emerge from people who bear envy and jealousy in their hearts and who create troubles and conflicts among people, thus, it is out of justice that they get recompensed with fire, a recompense that suits their nature.

{But those who reject Our verses and show arrogance towards them, they are the people of the Fire, they will abide therein forever.} [311] Surat al-A‘rāf: 36.

Allah's attribute of justice entails His being the Avenger besides His being the Merciful. Allah, in Christianity, is love only and in Judaism, He is wrath only; however, in Islam He is a just and merciful God to Whom all the beautiful names belong, which are the attributes of beauty and majesty.

In real practical life, we use fire to remove impurities from the pure substance like gold and silver. Similarly, while bearing in mind that Allah has the highest attributes, Allah Almighty uses fire to purify His slaves in the Hereafter from sins and misdeeds. At the end, Allah brings out of Hellfire whoever has an atom's weight of faith in His mercy.