He thinks he might kill her again if it comes down to her or him. He thinks he might be the one to pull the trigger rather than give the orders to the hangman and Athos is hardly sure how to feel about that. "I believe part of our vows was until death do us part. Given that she is alive, I do think I owe her some of my suffering. And perhaps I bear her sins, as well. Never get married," he instructs.