The Companion's quest "Hired Muscle" (one of the early quests in the Companion's quest line) had me going to Belethor's general store in Whiterun to rough him up (not to kill, otherwise you fail the quest). So I selected the dialogue option to rough him up (brawl) and the fight began.
I beat him down enough so he would surrender and I spoke to him again. There were no dialogue options other than to brawl again... so I did. And this time... he pulled out the Staff of Magus!! See, I'm a High Elf and I've done all the Winterhold mage quests. I really had no use for the Staff of Magus, therefore I sold it to Belethor for the extra scratch. And now the bugger was using it against me! But this time, he wouldn't surrender. He just keeps attacking until I kill him.
The thing is, I don't WANT to kill him, as he's my go-to guy in Whiterun to sell off misc goods that I don't need anymore. It seems like the quest just refuses to end until I kill him. There are no dialogue options indicating that he surrendered. Help!