This is like a Greek tragedy. Everything Michael says is a foreshadowing of Mary's death. She loves him unconditionally, and she is clearly his favored child. Hetells Mary he would burn in hell before he would see her hurt. He repeatedly tries to justify himself to Kay (and to himself) by claiming the life he lived was "to protect my family." His advice to Vincent? "They'll come after what you love the most." Then when he goes to confession and eventually repents over the corpse of Don Tomasso, he says if he is given a chance to redeem himself he will "sin no more." Well! There is a price to pay for redemption, and Michael's price was watching his daughter get murdered. It lays bare his rationalizations, and not only does he lose his child, he finally sees that the life he chose...the life of crime...was a meaningless life. That everything he did all the scheming, all the anger, the killing, the manipulating, the accumulation of wealth meant nothing. That is why he dies a broken man, alone in a dusty garden in Sicily.