My first character was a complete bastard. I only spared Megaton because it was more fun killing and/or enslaving all the inhabitants myself, I took whatever I wanted and plastered everything I didn't want with frag mines just to kill everyone that might take it.
My second character was... sort of inconsistent. After she blew up Megaton to get into Tenpenny Tower, her dad berated her. Shortly after, he died, which caused her to have a change of heart. She joined to regulators and has the highest possibly karma level as a result from all the raiders and Talon mercenaries, but still is perfectly willing to kill or enslave anyone who doesn't tread her right or generally seems like an evil person. She's sort of like Fallout's version of Judge Dredd.
My second character was... sort of inconsistent. After she blew up Megaton to get into Tenpenny Tower, her dad berated her. Shortly after, he died, which caused her to have a change of heart. She joined to regulators and has the highest possibly karma level as a result from all the raiders and Talon mercenaries, but still is perfectly willing to kill or enslave anyone who doesn't tread her right or generally seems like an evil person. She's sort of like Fallout's version of Judge Dredd.