Additional to this, Fredo's death olbviously was his remarkable sin. He slew Fredo, who is probibly the most innocent and sweetest character in the series for a weakness of character, that made him, who he was.
Innocent?? - "he KNEW it was gonna be a HIT"
No one wants to kill their brother but if you brother is trying to kill you - what do you do?
"What I want.... whats most important to me... is that I have a guarantee" - Train approaches.... Bang! Bang! Bang!
