I've killed a lot of people, but they DID start it... most of the times... sometimes... occasionally.
I think this game should have an option to let defeated enemies live. Currently, if the enemy has low health, he just kneels and begs for mercy. As soon as his health regenerates, he starts attacking you again. I'd love it if we could really let them live and they wouldn't attack you after that (Or some would, but not all).
I started a thread about that a while ago.
I've since noticed it does sometimes work, but never seems to with bandits. I've had that random encounter thief who demands money yield a couple of times, then make some comment (about letting you off or something - I can't remember) and stop being hostile. I've also put the smackdown on that guy who randomly shows up after the sanguine quest demanding money and had him stop being hostile after yielding.