Antagonist
Character Role Analysis
The Vicario Brothers? The Town? Honor? Angela Vicario?
It's really hard to say exactly who the antagonist is here. The antagonist is whoever is in opposition to the happiness or the goals of the protagonist. So by choosing an antagonist, we are basically assigning the blame for Santiago's murder. You can see why this is kind of difficult.
It would be easy to say that the Vicario brothers are the antagonists. They did kill Santiago after all. But why did they kill him? Because of Angela. So is she the real antagonist? But even if Angela pointed the finger at Santiago, and the brothers attempted to kill him, the town still could have stopped the murder from happening. So is the whole town to blame?
There's no easy way to answer that question, so we'll have to leave the antagonist position with a giant question mark instead of a name.