It seems to me that Neri did screw up once. I know a lot of you have never sat through the entire GF3 movie, but I believe Al's biggest, and only mistake, was when he went along with Vincent and Connie about the hit on Joey ZAZa. I think he was a reluctant party to this, but he, as the others, feared Michael was dying and the hit would be the only way to preserve any hope in the future for the Coreleone family to make a comeback.