User blog comment:Savannah Star/Michael vs. Lucifer/@comment-74.136.230.69-20130811053554

I think it depends on if Lucifer "insured" this fight. Keep in mind that Lucifer controlled Death at this time, unless he was playing fair, or just didn't think about it, he could have commanded Death to keep him from dying, which would make this an inevitable stalemate since I doubt Lucifer could actually kill Michael. Ultimately it's just a question of how effectively Lucifer uses Death, who's the most powerful force seen in the show, if he was immune to dying (which seems possible since Castiel paused when Dean revealed that they wouldn't die if "god pulled the trigger") then he could resort to just commanding Death to kill Michael, which would result in Michael's immediate death.