Like Squashing A Bug
A character does horrible things to others with the nonchalantness of someone stepping on an insect
Most people in fiction treat hurting or killing someone as a pretty big deal and have a similarly large emotional response to it. Not this guy. This guy could murder you eight ways to Sunday without any significant reaction or feeling during or afterwards. Maybe he's a sociopath, maybe he's been completely desensitized to violence, maybe he's been lead to believe you aren't actually living or real, all you know is he treats the act of killing you like a kid would treat the act of breaking a toy he didn't play with anyway. Most common with executioners, assassins and the Soft-Spoken Sadist, this trope refers specifically to a character commiting a murder or other harmful act and going about it with extreme coolness and detachedment, and afterwards having no strong reactions or memories to the act. Often the sign of at best an extremely battle-hardened warrior, at worst an apathetic Complete Monster who destroys lives as often and easily as any routine chore. Goes hand-in-hand with But for Me, It Was Tuesday. Examples:
- In the animated movie Superman: Doomsday, Lex Luthor asks his assisstent Mercy if the evidence of their involvment in the events leading to Superman's apparent death is covered. When she assures him yes, he shoots her in the head almost as an afterthought.
- Rarer non-villainous example in the film adaptation of RED, Hero Antagonist CIA Agent Cooper calls his wife and kids to wish them a good day, while in front of him there's a guy tied up and standing on a chair with a noose around his neck. He hangs up, pulls the chair from under the man, and calls his boss to let her know he completed the assignment all without missing a beat.
Hello, Unknown Troper. You'll need to get known to lend a hand here.