I'll add that Tom raises his voice several times with Sonny and contradicts him without fear. He never does with Michael and seems to be feeling a bit threatened when questioned about the Vegas job offer.

I think by the end of II, everyone is afraid of Michael. Tom sees he's like a barely restrained animal underneath that veneer of calm. Sonny could be violent and temperamental, but he wasn't cruel. I think Tom knew Michael was cruel, in a way neither the Don nor Sonny were, and as such, feared him - Or what he COULD do.

Sonny and Tom are brothers. Fredo is the kid brother they look after and love. Michael is, always was, and still remained the odd man out. Even with Sonny, he seemed awkward and distant and that's his own blood brother. Like, in 1940s scenes before Sonny is killed, Michael just seems a step removed from his brothers emotionally, not even just from the Mafia business.

He deliberately distanced himself from his family because he wanted no part of their business. He showed some real warmth--playfulness--with Kay in a deleted scene in a NYC hotel room just before Vito was shot. He opened himself up enough to be hit with the thunderbolt when he saw Apollonia. But, after that, he was cold as ice.

I think this is right, though I think "cold" might be more precise. It all runs back into the novel - Michael the mathematics professor, the rationalist. Kay loved him because he was "always fair," but she didn't realize his fairness could turn him against you if you failed him, and that everyone would fail him eventually.

I'd go so far as to say Michael is probably one of the best depictions of a pure sociopath ever put to film.

Everything to him is a deal. An arrangement. Other people are truly just players on his stage, nothing more or less. If they fail or succeed either way he will use it to HIS benefit, even if it comes at their expense. All human interactions he has after Sicily are business transactions. Even his interactions with his children in II seem almost calculated, like a man who is trying his best to act in a way society deems as fatherly - but even then there is a strange remoteness even to his small children, almost like a robot mimicking human behavior. The scene with Kay when she talks about their life doing some unspecified psychological damage to their son shows he doesn't care - "I don't wanna hear about it!" - it's more a wound to his pride that there might be something wrong with his son, than it is a matter of concern to him (whereas we see Vito is genuinely disstressed when seeing Fredo sickly as an infant).

I think every relationship in Michael's life - personal, romantic, or business - was sort of this highly calculated, highly manufactured facade, a mathematic equation, a transaction. Nothing more. Like he has no genuine interior world of emotion; no empathy. He is able to play easily on others' empathy (IE playing on Connie's sympathy for Fredo, and manipulating her into being unwitting bait for her own brother's execution) and exploit their human feelings for his own need. This is a man who hugs his brother warmly at their mother's wake, while giving the nod to Neri that the time has come to murder him. Even Vito, even in his coldest moments, was never so evil.

This is why in the original ending of 3, when Michael dies alone and broken, I don't feel sympathy as Francis wants us to. I think, good, you got what was coming to you, prick.