Wow! As many times as I have watched GF I almost feel "ignorant" or unworthy to even reply to Turnbull's excellent analysis.
I always wondered how a "nice college boy" could suddenly change and become a heartless villian he later became. I think Sicilian Babe is right, that after the Sollozo/McCluskey killings, Michael actually enjoyed it, whether it was the attempt on his father's life, the challenge of revenge or the power, that changed him, I don't know. I agree that he surely did become "devoid" of feelings tho. Which would make one wonder, was he always like that deep down inside, but didn't know himself what he was capable of, or can one event "turn" someone into a completely different personality. Yes, the tragedies Michael encountered in his life were mostly brought on by Michael.
TIS
"Mankind must put an end to war before war puts an end to mankind. War will exist until that distant day when the conscientious objector enjoys the same reputation and prestige that the warrior does today." JFK
Which would make one wonder, was he always like that deep down inside, but didn't know himself what he was capable of, or can one event "turn" someone into a completely different personality. Yes, the tragedies Michael encountered in his life were mostly brought on by Michael. 
