I agree that Michael was never a very warm person, but IMO his coldness grows as he transitions throughout the movie.
Basically what I am saying is I don't believe when he first began as Don he would've been able to order Fredo's death. But by part II his heart was completely cold.
And everything and everyone in his life were just pieces in his chess game.

wink Ace

There are things that have to be done and you do them and you never talk about them. You don`t try to justify them, they can`t be justified. You just do them. Then you forget it.