What is the ruling on insulting Allah Almighty, whether in a state of anger or not, and how does one repent from that? And is a Muslim rewarded if he forbids one who insults Allah, and if he dies from being beaten due to his forbidding, will his end be good?

Whoever intentionally and knowingly insults Allah has committed an act of disbelief (kufr) and exited the fold of Islam, whether he was joking or angry. This is based on Allah's saying: "Say, 'Is it Allah and His verses and His Messenger that you were mocking?' Make no excuse; you have disbelieved after your belief." His repentance is accepted if it is sincere and truthful. Forbidding the insulter is a religious obligation (wajib shar'i) and is a communal obligation (fard kifayah). Whoever is harmed should be patient, and whoever dies because of it, we hope his end will be good, and he may be considered a martyr.