Here are some points I took away from this article on violence.
1. Very few people are actually prepared for a life-or-death, organ-stabbing fight. “Herein lies a crucial distinction between traditional martial arts and realistic self-defense: Most martial artists train for a ‘fight.’ Opponents assume ready stances, just out of each other’s range, and then practice various techniques or spar (engage in controlled fighting). This does not simulate real violence. It doesn’t prepare you to respond effectively to a sudden attack, in which you have been hit before you even knew you were threatened, and it doesn’t teach you to strike preemptively, without telegraphing your moves, once you have determined that an attack is imminent.”
2. All other things being equal, I would imagine someone that’s pretty mild-mannered and hasn’t been in many fights would probably have quite a learning curve as a superhero. Most violent criminals (e.g. supervillains!) are used to violence that most people could not fathom. In a savage fight, it is very possible that a superhero’s mental/moral hesitations and inhibitions and unfamiliarity with violence could be disastrous. Superhero organizations might want to have new recruits fight nonpowered criminals in relatively low-stakes cases until it looks like they might be mentally and physically hard enough to survive a psychotic killer like Mr. Freeze or a death camp survivor that mentally ripped a foe’s tooth out of his mouth… back when he was a protagonist. And, let’s be honest, it’s not likely that every would-be superhero can successfully make that transition. (If you’re writing a larger organization like the Justice League, what does the group do about heroes that are so ill-suited for combat they will probably get themselves killed? For example, maybe some get retrained as crime-solvers and partnered with ace combatants and maybe others get let go and maybe still more take on important support roles like medic or scientist or whatever that might involve some exposure to violence but aren’t as intense as actually being a combatant).
3. Although I think the author discounts the potential benefits of bravery, I agree it definitely has potential costs. I don’t think we see very much of that in most superhero stories. For example, violence for Spider-Man is sort of Disney-fied–virtually the only permanent costs of violence (Uncle Ben’s death) are caused by not being brave. For most superheroes, I think the violence is heavily romanticized. Being a superhero is more or less fun and games except when a (usually secondary) character dies and, let’s face it, he will probably come back anyway. On the other hand, I personally don’t enjoy deep-R violence and would feel uncomfortable including it in something primarily meant as entertainment. (For example, in Kickass, a gangster gets crushed in a car-compactor–it’s decidedly unpleasant and I’m sort of annoyed it was a laugh-line for the audience).
4. It might be dramatic to make a hero choose between his pride and other goals. For example, if 3+ muggers have guns drawn on Bruce Wayne, it’d be pretty banal for Wayne to flawlessly disarm the criminals and walk away completely unscathed–pretty much every superhero would do the same in that situation. It might be more interesting if the character allowed himself to be robbed, walked away and got his revenge later. How much is his pride worth? Alternately, if the character does decide that his pride is worth risking serious physical injury and/or revealing that he has superpowers, have him pay something for it. (For example, the first sign to Gary that something is not right about his coworker Dr. Mallow is that Gary witnesses several men rob Dr. Mallow, taking among other things a cherished personal memento. Over the next several weeks, all of the assailants end up in mysterious accidents and the good doctor has his memento back. Mallow could have just let it go, but trying to protect his property even after the fact bears a cost for him).