The very last scene when Lorenzo comes to Sonny's wake. He thanks Sonny for getting C out of the car and saving his life and admits he never really hated him, he just resented him for making C grow up too fast. He then prays for mercy on his soul.
After Sonny wrongfully accuses C of being a part of a plot to assassinate him, he stops C from going along with his punk friends to attack the black neighborhood, thereby saving him from burning to death when the plot goes wrong. Made more poignant in the musical where C notes that, for all of Sonny's talk about making decisions based on fear, this act was one of love.
In a change of pace from films of this type where the mob takes kids under their wing as a recruiting tool, Sonny makes it clear to everyone that he does NOT want C to become a gangster like him and he would be better off getting an education and living an honest life.
Jane passing the test and opening the car door for C.
Lorenzo finally calling Calogero "C" as they leave the funeral parlor and walk home.
From the musical in the last scene, when Carmine tells C he'll be taking over the neighborhood and C can stop by if he needs anything, C tells him he thinks he's gonna give the bar a break. Carmine tells him he's glad to hear that. It's exactly what Sonny wanted.