Throughout the MCU, we have seen different characters with their own approach to heroism. Hulk runs from his ablities, Cap uses them to fight Nazis, Daredevil doesn’t even see himself as a hero at all, and Star Lord does… well… Star Lord things. Doubtlessly, however, each different hero does things a little differently. This is most notable in their attitudes toward taking a life.
In the comics, almost all the heroes didn’t kill anyone at all. They felt heavy weights of responsibility when it came toward the lives of those around them. Tony Stark even went on a war to reclaim his technology that was killing others. The only exceptions to this were Punisher, who was more of an anti-hero anyways, and Wolverine, who later reclaimed his soul, so to speak.
At one crucial point early in Frank Miller’s Daredevil, Daredevil found himself in a battle with Bullseye. Bullseye was wounded and on the train tracks. Daredevil wanted to leave him on the tracks to die, but knew that as a hero he had to save him. After surviving this encounter because of Daredevil, Bullseye went on to kill two of Daredevil’s closest love interests. No good deed goes unpunished.
In later days, the line has been blurred somewhat, with characters like Deadpool being praised for their violence, darker stories in comics, and more death as a whole. Despite these trends, most characters still abide by the no-killing rule as the line that separates hero from villain.
That being said, the Marvel Cinematic Universe has a much different take on the idea of killing. The Avengers have very little problem killing their enemies, especially if they find that there’s no other logical means. Iron Man has killed Obadiah Stane and Ivan Vanko in Iron Man 1 and 2 without hesitation. Thor holds off on killing his brother, but chops Malakeith into pieces using portals. Captain America is a soldier, so his unashamed use of SHIELD bases to launch bad-guys off ships shouldn’t be too surprising, but it’s rarely even touched on.
There is the notable exception of the Hulk, who despite being responsible for many deaths through the Incredible Hulk, spares the life of the Abomination at the last moment, due to the pleadings of Betty Ross. He remains one of the only villains to live through the end of the film (exceptions include Loki, Justin Hammer, and Winter Soldier).
The Guardians also have a decently laid-back mindset regarding killing. While yes, most of the killing came in form of larger battles, of five of the Guardians did their own fair share of destruction. Most of it was done with a laughable tone, such as Groot puncturing a dozen guards, slamming them against walls, and then smiling for the camera.
All together, these characters basically demonstrate a nonplussed reaction to killing.
Outside of the movies, the Defenders are apparently holding different ideas on the matter of killing. Despite a notably darker tone, Daredevil struggled with the idea of killing the Kingpin. It was one of the major themes of the TV show. Whereas Iron Man may have simply tank-missiled through Fisk’s protective jacket, Daredevil chooses to spare Fisk in the end. This is a drastically different mindset than that of the Avengers.
Whereas the uniformity of the comics across their characters meant that all Heroes followed similar ethical rules, the MCU has presented some of their characters with higher ethical standards than others in regards to the value of life. While this is reasonable, considering the numerous backgrounds of the characters contained, does that mean that some of the characters would even see each other as heroes? Daredevil doesn’t even see himself as a hero, so what would he think of a character like Cap, who regularly kills without a second thought?
Which standard of practice is most consistent with a true hero mentality? Can one be a hero while killing without hesitation? A part of me wonders if Steve would have been able to lift Thor’s hammer if he had not kept such a soldier’s mind on the treatment of life.
These questions are interesting for the development of the characters, but I don’t expect they will be addressed in more than a passing way in the future of the MCU. Undoubtedly, the question of killing will be further explored with the introduction of the Punisher in Season 2 of Daredevil. For now, only time will tell.