Have you ever noticed that in super hero movies, the hero, being a the personification of good, never really "kills" his arch enemy, the villain? Even though the hero has this thriving urge to aniquilate the bad guy (and we all do too when we're watching the movie), he'd rather catch him with life. If, by chance, the villain dies, he simply dies in a way that was impossible for the hero to prevent his plunge to death.
Have you ever thought about it? It´s a matter of principal: if the hero actually killed the villain then he would be nothing different from the villain.
We don't have television, so we don't watch the news. Which sometimes makes me forget that I'm even living in the United States. But the other day we were listening to the radio in our car and the local news comes on: this man is going to be executed on July 18th, here in Georgia. An then I'm remembered that I now live in a country were there is no difference between hero and villain.