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.
Agreed. Al went along because of his loyalty to Michael. He didnt want Michael killed(Corleone family to perish)(ala Michael wiping out 5 families to save Vito) albeit on a much smaller scale.... same preservation in mind.
The question: How could Michael have a former cop in such a high position?
The fact that Neri was of a certain mold AND had nothing else. He was forever indebted to Michael and family.