What must be done to soothe the questioner’s anxiety about her deceased brother, whose facial features were reportedly angry and whose body turned blue at the time of his death, and about whom she later learned that he died two days after a violent quarrel with a neighbor? And is there a fear of him suffering torment in the grave if his striking the neighbor involved injustice?

Your brother's death is not necessarily connected to what was mentioned, for death comes suddenly. If his injustice to the neighbor is proven, then search for the neighbor to seek his forgiveness and ask for pardon for your brother. If you cannot find him, then the right will be taken from the unjust person's good deeds on the Day of Judgment, as stated in the Hadith: "Whoever has wronged his brother concerning his honor or anything else, let him seek his forgiveness today before there is no dinar or dirham. If he has good deeds, some of them will be taken proportionate to his injustice; and if he has no good deeds, then some of the sins of his companion will be taken and laid upon him." In this case, increase your acts of seeking forgiveness, giving charity, performing Hajj, and 'Umrah on behalf of your brother, so that he may have good deeds with which to settle the rights.