...and to Michael's enemies. Michael always felt he had to communicate to foes that no one gets a pass from Michael Corleone. That was one of the reasons he had to get rid of Pentangeli and Roth, even though they seemed to be defeated.
TB, who knew of Fredo's perfidy? Roth, Ola? They were both pre-fratricide deceased. So, to who was Michael illustrating his ruthlessness by murdering Fredo? Perhaps the answer to that is that once Fredo's murder circulated through the underworld, the reason for it would then have then become known. But, what would that have accomplished? What incremental fear of Michael Corleone would have ensued as a result? I don't see it. Compared to the enormity of fratricide, what advantage did Michael gain?
He got rid of Pentangeli and Roth because it was well known throughout the underworld that Pentangeli had betrayed (quite publicaly) Michael and the other wanted him dead.
