So in Fallout 3, I just slaughtered the entire town of Paradise Falls (when I couldn't be arsed to do the mission where you collect the slaves) to set free the kids in the cages. Every street, every shop, dead, which makes me feel extremely pleased with myself, as it took much trial and error.
The thing that boggles me though; I did not lose one speck of karma. Infact, I actually fucking gained some for killing this one black dude that was in a heart-shaped bed with a slave. I didn't even know who he was, how was that ever a good deed?