Marvel Cinematic Universe/Fridge

Fridge Logic
Seriously, pay some attention to the films before asking ridiculous questions like this.
 * Of all the movies featuring The Avengers so far, why is Iron Man the only one who kills his archenemies? Thor is a warrior who's probably been taught to kill since he could hold a weapon. Captain America is a soldier. The Hulk is a berserker whose killings can be attributed to his animal-like nature. So why is Tony the only one whose enemies end up dead?
 * Did you not pay attention to any of the movies? Thor's "archenemy" is, you know, his little brother. Most people are hesitant to kill their siblings, especially when they spend the whole fight desperately trying to talk said little brother out of the fight. The Red Skull, we don't know what happened to him, but if he survived, it wasn't because Cap held back. Steve was trying to kill him the whole time. The Hulk, did you not watch that fight? The part where he's clearly about to kill Blonski but seeing Betty makes him stop?

Fridge Brilliance

 * The first four movies before The Avengers were all about someone having the ability to be an hero but not the qualities until he had to step up to the challenge: Iron Man was about the egotistic genious billionaire Tony Stark seeing first hand what his weapons were doing to the innocents and being unable to use the normal means to stop it, so he had to use the Iron Man armor to stop the terrorists (and Stane) and destroy the weapons himself; The Incredible Hulk was about Banner trying to cure himself of Hulk until Abomination entered the frame, at which point he renounced to any future attempt to get a cure so he'd be able to stop him and any other possible gamma monster; Iron Man 2 was about a dying Tony choosing Pepper and Rhodey as his successors as CEO of Stark Industries and Iron Man and getting them to step up to the challenge; Thor is about Thor stopping being selfish and learning humility. Then we have Captain America the First Avenger, that is about the opposite: Steve wants to make a difference and stop the Nazi, but first lacks the powers (being a skinny runt before becoming the Super Soldier) and then the occasion, and has to take them, becoming an hero in the process.
 * Some might wonder why Coulson simply didn't shoot the robbers A Funny Thing Happened on the Way to Thor's Hammer. Well, police are a lot more interested when a couple of punks end up with bullet holes than they are when some mystery man simply beats them up.