The scene near the end when Brian decides to battle the blaze on his own to rescue the firefighters he needed to rescue a dying Stephen. Just the way he battles the fire is awesome personified because it's shot in a away that he is fighting a demonic force of hell and it's losing. Stephen whom throughout the entire movie refused to take Brian seriously watches in awe as the fighters make it to him. What he said also becomes a crowning moment of heartwarming.
Stephen: Look at him, that's my brother goddammit.