As far as simply fearing for your life, Santino was indeed the BIGGEST threat, at least while he was acting Don. With Vito and especially Michael - you knew you were risking your life if you messed with them, but you COULD do business it you kept one step ahead (which Barzini & Roth at least TRIED to do). That was the business you had chosen.

Sonny was all temper, all violence, little or no reason. He would have you whacked for looking at him the wrong way and that is why he could NEVER have been a successful Don.

But the nice thing about Sonny (besides feeling bad if he insulted you) is that camera he'd gladly pay you back if he broke your camera.

Apple