Only for certain kinds of people, for most, you have to undergo rigorous training and indoctrination to even get in the right mindset to deliberately end a life. 

When it comes to superheroics, you can't really compare it to any other kind of combat. Any kind of battle outside a training room or a street brawl is a kill or be killed situation, and while a certain amount of luck is there, the most skilled tend to survive. 

In comic book situations however, their powers and abilities allow them to end fights without killing, which is something that real life people just can't do reliably like comic book characters can. And in comic books, fights are pretty much started over everything and permanently ending the opponent isn't the goal. They have the luxury of taking people alive. In the real world it often does not work out that way. 

I don't think that's germane to what you're actually saying though. On a certain point I kinda agree, you have to be a real badass like Batman or Daredevil to take down guys without killing them. But the best killers have skill and artistry that rookies and novices don't have, like Deathstroke or John Wick.