John Wayne's Acting
I know that his acting in this is almost universally praised. But I think there was a huge flaw in his acting.
I think one of the coolest aspects of the film is the idea of a strong-willed but fair and straight man "losing it" due to dire circumstances. I think that we should therefore seen a more visible transition in his demeanor from stability to unstability. I think Wayne largely fails at this.
Think for example of Bogart's Fred C. Dobbs in "Sierra Madre". Or think of Bogart's Queeg in "The Caine Mutiny". Bogart clearly manifested the expected character traits of someone who is becoming unhinged. I don't think Wayne had the range to allow himself to stray so far from his sturdy, all-American, can-do character.
(I personally find Bogart's performances in both these roles flawed, but I'm certainly in the minority on that, and anyway, that's not relevant for the main point I'm trying to make here.)
As a similar example, I think that Tom Cruise did better than Wayne here, but that he also did not portray as well as it could have been done, on the transition from goof-ball to serious lawyer in "A Few Good Men".
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