I think we are al in agreement that "danger" as seen in all three movies posed an existential threat. What is kind of
peculiar is that in GFI this threat is manifested by Barzini, using Sollozzo as a means to bring down the Corleone family and take over as the DOn of Dons.

By the time of II, we see what a visionary Michael was in that
he was moving past the olive oil business Barzini had so coveted and expanding the operations into Nevada and Cuba, and in the process himself posing an existential threat to the Corleone Family (Mama: You can never lose your family... Michael: "Tempi cambi (times change)." By the end of II there really was no "Corleone Family," per se, just Michael.

By the time of II it was all about Michael and the threat to his greed and ambition that posed the "danger."

So as the "face of danger" changed in all three pictures, so did the nature of the danger, and the entities to which it presented itself.