... Michael himself clearly regretted killing Fredo later in life. In his confession to Lamberto, he explains the killing by saying "he injured me." Not, "he was a danger to me" or "he turned against the Family." ...
While it was a well done scene and nice to refer to ... it's almost silly to factor anything in GFIII into this discussion.
Much GFIII was simply a wink and nod or to placate loyal fans of GF and GFII.
While of course Michael would regret it 'later in life'...he may have also regretted it a week later. He may have regretted it the moment he hung his head at the sound of the gunshot. His remorse isn't the point. The point is he handled Fredo's betrayal the way it had to be handled. By eliminating the traitor.
