Kay had accepted that he was a Mob Boss even that he was always fair
I think this goes back to the notion of Michael as the intellectual brother who intended to be a math professor. Fairness doesn't necessarily mean generous. On the one hand, it precludes him from acting with malice, but on the other it precludes mercy. No matter who you are, you get out of Michael what you put into him. Unfortunately, everyone else is human, so they'll all fail Michael in the end.
1. He took care of his father
2. mother lived with them
3. invited Connie to stay with the family, having everything she wanted
4. He was prepared to work on their marriage with Kay
5. always took care of Fredo
6. large dowry for Sonny's daughter
I reckon, people acting with malice cannot be shown mercy especially in their kill or be killed world and for repeated offenses
And a man in his position can't afford to be made to look ridiculous!
