Oftimes this process of self-examination is mostly unconscious. You don't have to kill somebody to create a believable character of an assassin, but you should be willing to create that character from a realistic, searching point of view, if necessary. Why does a person kill another person, and especially, as a profession? What moral or philosophical resolve did such a person make to justify their job? What kind of skills and training does it take to become a hired killer? How do you feel about hired killers? Is their ever a case where assassinating somebody is justified? Action films are often thought of as two-dimensional in their exploration of their characters, yet there are several wonderful character studies of assassins on celluloid: "The Mechanic," "Le Samourai," and "The Professional" all come to mind. All of these films have a distinct point of view about the world, and all of them have completely different takes on who their assassins are and why they do what they do. Because of their underlying philosophies, they all transcend their genre to become greater works. And surely, the writers of these works weren't necessarily always conscious of the fact that their works were a mirror of their own values. Each of these films end with the killers being killed, as if to reinforce the idea that what the protagonists did was wrong, and are thus reflections of their writers' values against cold-blooded murder. Certainly, there exists no rule that says that these films had to end this way, just as there was no rule to tell Shakespeare that Hamlet needed to die at the end of his quest for vengeance.

All of this is a roundabout way to say that via self-examination and self-knowledge, you can write work that is memorable, deep, and worthy of your time as a writer and an audience's time in the theater.

Your stories are you. And who are you?