One of the holes in the storyline is that Michael obviously ordered the killinig of Tessio, who was Clemenza's equal. The buffer IMO was Tom Hagen who is the only ranking family member present when Willie Cicci himself takes Tessio on his last car ride.
"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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