Sorry, but I wholeheartedly disagree. I think that Fredo's anger goes way beyond that. As for Michael being compassionate, there is no room for that. Fredo, intentionally or not, almost brought about the destruction of the family. Why? Because he was passed over?? Tough noogies. Having been brought up in the business, there is no way, consciously or not, he did not perceive that there was some evil inherent in the deal Roth offered him. And it would be impossible for Michael to forgive that.

While Cristina touched on the fact that Fredo was jealous of what he didn't have, there has to be the understanding that it was something he would NEVER have, something he was incapable of achieving. His resentment was not only for the fact that their father passed him over for Michael, but that he could never BE Michael. He wanted the power and respect that Michael had, but he was both unwilling and incapable of putting in the time, effort and hard work that it took to achieve it.