Are all Christians eternally in Hell, and is the judgment of burning with fire in Hell very harsh, which might imply that the questioner has a poor opinion of Allah?

It was previously stated that the People of the Book are disbelievers and what their destiny will be in the Hereafter, and that Islam is the true religion. No one will remain eternally in Hellfire except for those who associate partners with Allah: "Indeed, whoever associates partners with Allah, Allah has forbidden him Paradise, and his refuge is the Fire," and "Indeed, Allah does not forgive that partners be associated with Him." Allah created mankind upon monotheism and took a covenant from them that they would not worship anyone but Him: "Every child is born upon the natural disposition (fitra)," and "Am I not your Lord? They said: Yes, indeed." Allah sent messengers as bearers of good tidings and warners, so that mankind would have no argument after them. Therefore, no one perishes concerning Allah except for those who choose to deviate from the path of truth. It is recommended to come to know Allah by contemplating the آثار (effects/signs) of His mercy and reflecting upon His beautiful names and attributes, and by reading books on creed such as "Al-Aqidah fi Allah" (Creed Concerning Allah) by Omar Al-Ashqar, accompanying people of knowledge, and supplicating for certainty, beneficial knowledge, and righteous deeds.