Funny, but that description of Michael happens to bring to mind a very young Vito (in his 'prime'), slithering deftly across the roofs of his neighborhood, preparing to corner and 'strike' a completely unsuspecting Don Fanucci.
Yes, that's true!
And you are right, all the Corleone's men had the same attitude, but Michael was the most rutheless.
I agree about Vincent, poor thing.