What is the ruling on one who likens himself to Allah? Is he thereby considered an atheist or an apostate, and should he be killed? And is he excused for such a statement if he was angry?

If a Muslim is an adult, sane, and acting of their own free will, not under duress, then whoever likens Allah to His creation has disbelieved, and whoever denies what Allah has attributed to Himself has disbelieved. The scholars of Ahl al-Sunnah wal-Jama'ah have unanimously agreed on the disbelief of the Ittihadiyyah (unionists) and the Hululiyyah (incarnationists). An apostate is to be subjected to the punishment for apostasy by the ruler, not by individual Muslims. An angry person is not excused as long as they are aware of what they are saying. This apostasy ends with a return to the religion of Allah, enjoining good and forbidding evil, and establishing the prescribed punishments.