Fom a Mafia Don's perspective, Michael makes two grave mistakes when dealing with Fredo. He breaks Don Vito's rules of "Keep your friends close but your enemies closer." and "Never tell anybody outside the family what you're thinking". In Cuba, it is quite clear that Fredo is the traitor and no "friend" of the family. After losing control of his emotions, Michael then kisses Fredo and tells him that he knows about the betrayal. Any other mafia family traitor, without warning, would have been dead in 24 hours or followed to find out who else helped him and revealed the balance of conspirators. Michael should never have told Fredo that he knew it was him. Fredo and his wife should have been moved back to the family compound immediately where he could be monitored. From a brother's perspective, Michael was indeed crushed and heartbroken - no doubt. Back to the original question...No, I could not have had my own brother killed. Great question, HX and wecome to the board.
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Regarding the quoted post, I think Michael did "keep Fredo closer." Yes he had the "I knew it was you....you broke my heart" scene, but shortly after he tried to get Fredo into his car to allow him safe passage from Cuba. Terrified, Fredo would not go. The first business move Michael made when he got back to Nevada from Cuba was to instruct Tom to get in touch with him, to tell him that things were ok, that Roth misled him, and basically that he could come home to Tahoe, which he did. Fredo lived there in comfort for some time. I believe Michael did not decide that Fredo had to be killed until the
"I was passed over" scene. What happened there were a couple of things. First, Fredo showed how much he resented Michael and the fact that his own father wanted him to be passed over. This demonstrated that Fredo had not lost any of the rage that led to his betrayal of Michael to Roth, and it meant that given the chance, Fredo would do it again.
Second, Michael learned that Fredo knew Pentangeli was alive. Not only did Fredo keep this to himself while Michael and Tom were prparing for the Senate hearings, but after the perjury trap was set he lied to Tom, claiming he knew nothing. Michael got Fredo mad, and obtained this information. This demonstrated that the betrayal was ongoing, and that perhaps Fredo wanted Michael to go to prison so he could "take over."
As a mafia Don, once this happened Michael had to have him killed. Note Michael did not give Neri the order until after that outburst.