The moment that inspired this question:
A long time ago I was playing an MMO called Voyage of the Century Online. A major part of the game was sailing around on a galleon ship and having naval battles in the 1600s.
The game basically allowed you to sail around all of the oceans of the 1600s world and explore. The game was populated with a lot of NPC ships that you could raid and pick up its cargo for loot.
One time, I was sailing around the western coast of Africa and I came across some slavers. This was shocking to me at the time, and I was like “oh, I’m gonna fuck these racist slavers up!”
I proceed to engage the slave ship in battle and win. As I approach the wreckage, I’m bummed out because there wasn’t any loot. Like every ship up until this point had at least some spare cannon balls or treasure, but this one had nothing.
… then it hit me. A slave ship’s cargo would be… people. I sunk this ship and the reason there wasn’t any loot was because I killed the cargo. I felt so bad.
I just sat there for a little while and felt guilty, but I always appreciated that the developers included that detail so I could be humbled in my own self-righteousness. Not all issues can be solved with force.
I remember the first mission of hotline Miami. You take the phone call and learn that you are supposed to kill some people. You learn how to use your guns. You kill a bunch of baddies, quite badass. Then at the end of the mission, the screen starts swaying more than usually, and the protagonist vomits in an alley. Of course, he just killed for the first time, overwhelming. Makes him quite human, more than many other protagonists, despite the pixel art style.