Michael was never more reprehensible than at his boathouse meeting with Tom, Rocco and Neri near the end of II:

TOM: Why did you ask me if something was wrong when I came in?
MICHAEL: I thought you were goin' to tell me that -- you were going to move your family to Vegas -- and that you'd been offered the vice-presidency of the house and hotels there I thought you were goin' to tell me that.
TOM: I turned them down -- do I have to tell you about ever offer I turn down?
MICHAEL: let's do business.
TOM: Alright -- just consider this Mike -- that's all just consider it. Now ROTH and the Rosato's are on the run -- are they worth it? And are they strong -- is it worth it -- I mean you've won -- do you have to wipe everyone out?
MICHAEL: I don't fell I have to wipe everyone out -- just my enemies -- that's all. You gonna come along with me in these things I have to do -- or what. Because if not you can take your wife, your family, and your mistress -- and move 'em all to Las Vegas.
TOM: Why do you hurt me MICHAEL -- I've always been loyal to you -- I mean what is this.
MICHAEL: So -- you're staying?
TOM: Yes, I'm staying. Now what is it that you want me to do?

So: Why did Michael hurt Tom--humiliated him--in front of Rocco and Neri? I’m tempted to say, “because he could,” and it wouldn’t be a wrong answer. But I think Michael, as usual, had additional reasons.

What do you think?