Mikhail

I'm really struggling with the fact that Mikhail essentially murdered Charlie.  I really wanted to believe that he wasn't so bad, and that Desmond did the right thing in letting him go.  In fact, I went so far as to think that the action constituted a life debt that Mikhail would feel honor-bound to repay if given the opportunity.  But his loyalty to Ben runs deeper than his debt to Desmond, and I suppose the fact that Desmond shot him with a harpoon would cancel out a sense of obligation...  And Mikhail probably didn't recognize him when he was shooting at him from shore.  Still, I thought he might save our friends at the last minute.  Instead, he did just the opposite.  They would have been fine if not for him.  So should Desmond have killed him back in the jungle?  (Would Mikhail have sprung to life again anyway?  If not, who would Ben have sent instead?)  Was mercy still the right path, even though it led to Charlie's demise?  It was one of those scenes that sort of makes me question my convictions just a little...