Well, there are many, MANY moments of brutality I've done in Red Dead Redemption, I really can't decide. It's either:
A. Tying up a poor Mexican woman, bringing her to the middle of nowhere and putting bait on her and watching her get mauled by coyotes from a distance.
B. Following a random stranger to help him rescue his brother from a hanging, wherein I shot the criminals, then shot the brother + stranger for interrupting me while I was hunting for treasure. Assholes.
C. Shooting a runaway criminal, accepting a reward from a nearby pursuing lawman, then shooting the lawman for the six dollars in his pants.
or
D. Shooting a man's horse so he was launched into a cactus face first. That wasn't planned out, tbh, but I'll be damned if it wasn't funny.