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.
Vindicated by History: The film is much more recognized now than at the time of its debut: in 1970s it was panned as the weakest Leone (especially in US), nowadays it is generally considered to be at least on par with the others (and some even think it's Leone's best film). The fact that the film was severely cut for US screenings certainly didn't help.