A small detail I noticed:

During and after the immediate aftermath of the assassination attempt, Michael at first shield's Kay's body with his own to protect her from being hit. After he asks her, worried, if she's hit, holds her and reassures her softly "it's over, it's over." In that moment, you get a final glimpse of the Michael we meet at the beginning of the first film - a last moment of human vulnerability. I have to think this was something intentional.

Ever since Michael greeted her at the schoolyard in 1951, their relationship as depicted is very cold, and only becomes chillier as time goes on. Michael is her husband; her owner; he is the Boss not only of his Family, but also of her and their family. They are but extensions of him. She is his wife.

Her questioning annoys him (where at one time, he voluntarily told family secrets to her, almost half amused and half embarrassed by them). They are a modern couple in 1945 at the wedding; partners. After he comes back, they are, at least Michael wants them to be, an old fashioned Sicilian man and wife.

But in this brief, brief moment of softness during and after the assassination attempt, he's Mike. For perhaps the very last time.