Brad Pitt did not receive an Oscar nomination for portraying Mr. O'Brien in The Tree of Life.
What is really the best part of the film really is the character of Mr. O'Brien as portrayed by Pitt, even though the film's treatment of the character does not quite work all that well. I mostly refer to the fact that at times it treats him like he is the worst father who ever lived, particularly in the scene with the son contemplates killing him. That actually just made me want to slap the kid because although he is not father of the year material by any measure, he certainly should not die because the son seems to hate even the slightest bit of strictness.
I think perhaps a problem in the depiction of Mr. O'Brien is that maybe Pitt gives too much of a complex performance for the way the film wants to represent the character. It is actually quite extraordinary that Pitt manages to give the performance that he gives considering the limitations brought on by the way Malick directs the film. It is always far more interested in scenery and spectacle of the world rather than the people in it, as the camera commonly drifts off faces, or to some angle that really would not be ideal for any actor in any film. This is probably contributes to why some actors, like Christopher Plummer, have a problem with Malick's methods.
To the absolute credit of Pitt though he manages to make Mr. O'Brien the most compelling character in the film even when the film commonly drifts from him, or even sometimes drifts away from him within a frame of a single shot. Pitt makes a stamp on the film whether or not the camera seems to want him to do so. He creates Mr. O'Brien into a father of the 50's in the manner he carries himself, and acts around the children. He is very much head of the household, and Pitt holds a command over the proceedings in any scene where Mr. O'Brien is with his family.
Even though the film gives Mr. O'Brien a ridiculously hard time for being human Pitt never once leaves Mr. Mr. O'Brien as just a one dimensional being for his sons to hate. What is so important about his portrayal is the warmth he does put into his performance. Pitt always makes it abundantly clear that he does love his sons very much in the way he interacts with them, and as well grieves over another one. It is a very moving portrait of a father who tries to do what is best for his sons despite the way his sons my view some of his behavior.
In the scenes like the one where Mr. O'Brien teaches the boys fight, or disciplines them in some way, Pitt never portrays any of this as random abuse. In his face, and his manner towards the boys particularly the way he really is always very encouraging, Pitt shows that Mr. O'Brien is trying to teach the boys valuable lessons, not just to punish them. Pitt always shows these as the lessons of a father who cares, whether he is right or wrong, the passion that Pitt puts into the part makes the character of Mr. O'Brien far more interesting because in reality he is not trying to be abusive in any way.
The big attack against Mr. O'Brien by his son is that he is hypocritical, and does many of the things he tells his son not to do. Pitt actually plays it well because in the way he portray Mr. O'Brien, he is actually aware of that. Pitt portrays a genuine sadness subtly in short but important moments over his own flaws and lost potential. Pitt makes it so it is not that Mr. O'Brien really is being contradictory, but rather Pitt shows that he honestly wants his sons to be better men than he was. He wants them to be able to reach places that he himself never could.
What is wrong with the academy when it comes to Pitt, I have not gotten to 1995 yet, but in both this year and 2008 they failed to nominate his superior supporting work in favor of his lesser leading work. This is once again a strange occurrence considering The Tree of Life was nominated for Best Picture, and the actual nominees were a sorry sort. It is a shame they missed this incredible performance by Pitt, that I think honestly went far above with the part. I really only wanted more of Pitt's Mr. O'Brien in the film, and it is truly astonishing how much he manged to do with this character despite the limitations set by Malick's directorial style.