Two scenes....1)Vito is lying in bed after he learns of Michael's role in the Sollozo hit, and 2) in II when Mike says "Fredo you're my brother, you don't have to apologize."....In these two scenes we see Fredo in retrospect, on one hand mourning the fact that he was too weak to save his father from the hit and the other scene in II w/ Mike he gives a look of silent frustration as Mike embarasses someone AGAIN...
I don't see anything 'complex' about Fredo in
either of the instances you are talking about. In addition to the fact that in GF time, they take place approximately 10 YEARS apart from each other.
I do agree though, that Santino also wasn't even remotely 'complex'. 'Simple' is the word to describe
any guy that would bang a bridesmaid at his own sister's wedding, with his own wife & mother right downstairs. At least Fredo waited until getting to Vegas to get at the ladies two-at-a-time!
Apple
