Does the death of my brother in an accident after a coma, and his raising of his index finger during his ritual washing, count as signs of a good ending and atonement for sins?

Raising the index finger while washing the deceased might be a sign of the declaration of Tawhid (Oneness of God). If the dying person uttered it, even in a whisper, then it is hoped that they are among those about whom the Prophet, peace and blessings be upon him, said: "Whoever's last words are 'La ilaha illa Allah' (There is no god but Allah) will enter Paradise." This applies to a child due to their few sins and Allah's vast mercy.