Keep in mind that Fredo knew the Feds had Pentangeli. And, after the outburst, he tells Michael that "the Senate lawyer, Questadt, belongs to Roth." That was info Michael didn't have. Had Fredo wanted to get back into Michael's good graces, he could have told him that long before Michael perjured himself five times. That tells me (as it must have told Michael) that, even after his perfidy was exponsed in Havana, Fredo was still unrepentant.
I agree. I think it was Fredo's outburst that got him killed.
When the revolution is about to set in and Michael yells to Fredo "Come with me, you're still my brother", I think he was sincere.
