There’s this misconception that in s5 Martin was bloodthirsty and wanted to kill. No, he didn’t. He just wanted these people dead. He didn’t want to do the killing himself. He used Jon to kill for him, so that he wouldn’t have to feel guilty about it. And I’m sure that if he was the one with the power to kill, he wouldn’t have been as eager to abuse it. Because then he would have to take responsibility for his own actions for once.