That moment for me would have to be Red Dead Redemption Undead Nightmare. During the sidequest Birth of the Conservation Movement, you are tasked to kill 6 sasquatches (Bigfoot). After killing the first five with surprising ease, John Finds the last sasquatch crying. The bigfoot looks at you and he starts speaking fluent english telling you how "some maniac" has killed off the sasquatches. John then justifies this by telling them that they ate babies. The sasquatch angrily says that they eat berries and mushrooms. The sasquatch resigns his fate lamenting that he is the last of its kind, how his family was killed by John. Then he begs John to put him out of his misery having lost the will to live because of you. You are then given a choice to either let him live and leave him to wallow in his misery or put him out of his misery. I actually felt sorry for what i did and chose to put him out of his misery.