Roth.

Sollozzo just wanted to have his narcotics, and if Don Corleone stood in the way... bad for him.

Fredo didn't know they were gonna assasinate Mike.

Senator Geary hated Michael, but he merely wanted to tease them.

It never was clear to me who the Lucchese guy was, what he did, what he had against the Corleone. If they just told he was a young button of Don Ciccio in the old days, then that would be fine. Stupid explanation, but then he at least has a background.

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See, we can act as smart as we want, but at the end of the day, we still follow a guy who fucks himself with kebab skewers.