Originally Posted By: Sicilian Babe
And yet Michael was only doing what his father couldn't bring himself to do - kill his daughter's husband and the father of his grandchildren. Although Vito wanted and needed to avenge Sonny's death, he didn't have it in his heart to actually murder Carlo (although he could apparently plan it) and hurt Connie. He left this unpleasant task to the far more ruthless Michael.


Well, maybe Vito couldn't kill the father of his grandchildren. Or maybe he had bigger fish to fry. Remember, he forswears vengeance for Sonny as part of his plan to:

1)End the war
2)Smoke out his true enemy
3)Arrange Michael's safe return

and, down the line,

4) Demonstrate the "weakness" of the Corleone family

Leaving Carlo alive made Vito seem both sincere and weak to the other dons, helping set in motion the series of events culminating in the assassinations of the heads of the Five Families.

"A man in my position cannot afford to be made to look ridiculous!"