More a sad story than a moment of remorse : A month ago I made myself a new character; A human male who loved a good fight, but wasn't all that much interested in killing random people for fun, preferring a true challenge to a simplistic murder. I then recruited a random guy who worked for the local lord, and by talking to him, I soon realized he had almost the same attitude and morals. We quickly became friend, and we traveled the world far and wide, looking for strong opponents to challenge. He saved my life a few times, killing enemies who were about to deal me a lethal blow and preventing goblins and bandits from ambushing us during the night. One day, as we were invading a dark fortress so that we could challenge the demon living in it, we were having the time of our lifes; We laughed in joy as the demon proved to be a greater challenge then anything we had seen before. As I was about to deal the final blow, the fiend threw a spear to my friend, piercing his chest. Thinking it was nothing he couldn't survive (He had once been badly beaten up by a Bronze Colossus and survived without any lasting damage after all), I ended the monster, and went to help him back on his feet.
I then realized he was dying. Rushing to his side, I saw that the spear had gone right through his steel breastplate and had punctured his right lung. I could do nothing as he struggled for air, and as he looked up at me, I knew that he would never allow himself to die like this. Offering him a more honorable (And quick) death, I stabbed him in the neck, mangling his spinal cord and making sure his death would be painless. A few minutes after he passed away, I decided to butcher him.
To this day (It's been many months in-game since it happened), I carry his skull in my backpack, defeating stronger and stronger opponents. I feel bad about not bringing him back to his family sometimes, but he was a warrior : He wouldn't have wanted to be buried in a cemetery, to be forgotten in a few generation; He would have wanted to be carried in battle, so that his afterlife could be spent doing what he liked the most : Fighting