Ending Fatigue: Especially in the restored version, with a final flashback that interrupts the climactic battle for several minutes.
Jerkass Woobie: Juan, who had been established previously as a bandit, rapist and highwayman, is also subjected to bullying and brutal verbal abuse from a group of racists while riding in the same stage coach as them. He fully crosses into this in the second act, after seeing his family killed.
Moral Event Horizon: Colonel Reza and the Mexican army cross it with the murder of Juan's children.
Surprisingly Similar Characters: Juan and Max Lozoya from Don't Turn the Other Cheek, which came out the same year. Both become revolutionary heroes by no will of their own and both had their families killed by soldiers. Also, as mentioned below, Eli Wallach was meant to play one but ended up playing the other.
What Couldhave Been: Eli Wallach was originally meant to play Juan, but United Artists wanted a bigger name, so they got Rod Steiger. Some foreign dubbing companies caught wind of this during the release of 'Don't Turn the Other Cheek' and had the same foreign actors voice both Steiger's Juan and Wallach's Max.