All to often we see the package deal and not the painfull emotion that accompanies the necessity of killing.
I know there are a lot of hangups about Captain America, but at the begining of his Marvel Knights run he killed a terrorist. And it actually showed some of the emotion that goes along with that. He went on camera saying "I did what I had to, he was a danger and my duty is to protect." Even though he was a terrorist and a badguy, it was still taking human life, and he was shaken up over it, which I thought made for a very powerful scene and story.