Michael's scream for sure....in fact that whole Mary death scene with Connie and Kay wailing, Anthony trying to comfort his mother and Tom Hagen's son praying...
Also I agree the very understated sigh Brando makes when Hagen tells him that Sonny is dead, which is followed by him walking over to Tom and putting his hand on Tom's head.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
"I stood in the courtroom like a fool."
"I am Constanza: Lord of the idiots."
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