In GF we see truly dangerous characters. First of all Vito's effect on Bonasera is Vito's effect on us: "And then they would fear you."
Solozzo radiates danger the first moment we see him. Also Luca Brasi. When he enters the Don's office, we feel the uncomfortable situation and that he could explode any moment. Also, since his return from Sicily, Michael. And to a certain degree Clemenza after he took the leak. (One could Sonny here, but I don't because he was like an open book. His danger was always immediate.)

But then during the trilogy we lose the number of dangerous people.

In GF2 we don't have a real equivalent of Sollozzo. Roth is more an equivalent of Barzini. Sollozzo is a panther. Roth is a cat.
Young Vito becomes a dangerous character, Michael develops his darkness. His body guard radiates danger, but he doesn't come close to Brasi.

GF3 lacks totally of dangerous characters. Don Lucchesi with his body guards is a laugh. Altobello doesn't have class. Mosca is like an old man, fumbling with guns. And Lupe looks like a fool. There's some potential in the twins. Zasa is ridiculous, and nobody ever cares about his "bulldog". Michael has become a nervous wreck. I would swallow a lot of inaccuracies in GF3 as I did in GF2, as long as I would care about the bad guys.