In the DC universe, most famously Batman has a 'no kill policy'. But so far every Marvel superhero I know has killed one way or the other.
So, is there any superhero in the Marvel universe who practices a no kill policy?
I don't want superheroes who avoid killing, but a superhero who has specifically said that he won't kill since it's in his moral code.
Answers from the movies, comics and tv shows are acceptable.