When the hero decides to spare the villain, only for them to be immediately executed by another character.
The Expanse S2E2: The heroes make the pragmatic choice to spare the villain. Miller expresses his disagreement with a bullet to the head. Then several more to make sure.
The Expanse S3E6: Amos talks down his friend from killing a scientist who hurts kids, because he's not a murderer. Amos, however, is.
Mass Effect: Wrex, the proud-warrior-race bounty hunter party member executes Fist if you spare him. In his defence, he does announce that he will the first time you meet him.
The Legend of Vox Machina S1E12: Percy, after almost (literally) losing his soul to vengeance, chooses to spare and forgive the woman who killed his parents. His sister is less forgiving, and cuts her off mid monologue.