No matter how hard you try, you can't kill Markov, he has 'plot armor'. See the link below.
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god is upon us
because when roach and ghost got the dsm from makarov's computer, shepherd just wanted the dsm he dint care about ghost and roach that why he killed em , he was just focused on makarov
he doesn't
Information linking Makarov to the massacre at the airport
You cannot kill Barney, as he is a fictional character. However, if Barney were a real person, you would go to prison if you were to kill him.