Call me crazy if you want, but I love the opening of the first movie. Bonasera is there...asking for justice. And there's Vito....the big, tough Don petting a kitty. I think that scene tells you a lot about what kind of man Vito is. Tough? Sure. But also kind and compassionate and capable of a great amount of gentleness.
I also love the scene where Sonny pounds the daylights out of Carlo for beating on Connie. "If you ever touch my sister again, I'll kill you." Brotherly love is a wonderful thing.