I played a good person in KOTOR one time, and an evil one 6 times. What does that say about me?
I even played through as an evil Sith whore named Swallow Cox.
I felt a little bad recently while playing Oblivion. I got to be kinda chummy with the other Dark Brotherhood members in the Cheydinhal Sanctuary. Then the time came when my quest was to kill them all. I talked to them all one last time, watched them go about their routines for a minute or two, then whipped out Shadowrend and sent them to hell.
The skeleton guardian didn't attack me though, so I let it live.