Will all misguided sects abide eternally in Hellfire? And does Allah's saying, "And We will remove whatever is in their breasts of resentment, [so they will be] brothers, on thrones facing each other" mean that all misguided sects will not abide eternally in Hellfire, and that punishment in Hellfire will only be commensurate with sins?

The misguided sects whose misguidance reaches the level of disbelief that expels one from the fold of Islam will abide eternally in Hellfire due to their disbelief, as Allah Almighty says: "Indeed, those who disbelieved among the People of the Scripture and the polytheists will be in the fire of Hell, abiding eternally therein. Those are the worst of creatures." Their entry into Hellfire is not due to their disagreements but rather to their obstinacy and disbelief in their Creator. They will be prevented from entering Paradise, as the Prophet, peace and blessings be upon him, said: "Indeed, none shall enter Paradise except a Muslim soul." As for the monotheists, Allah will honor them by removing rancor from their hearts and establishing brotherhood among them.