If Part III should be appreciated for anything, it's that it succeeds in making Michael Corleone a tragic character. At the end of Part II, we see he's troubled by what he has done -- but we also get a sense that he still believes that everything he has done to that point has been necessary to "protect the family."

In Part III, he clearly see that Michael regrets killing Fredo -- as well as ordering the deaths of many men. Michael's past comes back to haunt him -- and while the details of the story aren't always perfect -- the whole is greater than the sum of its parts.