If you’ve played combat-based RPGs or video games for a while, it’s easy to forget that in the kind of world where superheroes operate, most people aren’t accustomed to violence. When someone starts shooting or crashes through a brick wall, most people are going to scream and run. You’re different, of course. You run towards the smashing and gunfire, but that’s part of what makes you a hero. Likewise, even those who might put themselves in the middle of violence, such as street criminals, are only rarely capable of actually killing anyone. Beating them up, maybe, but not killing. Most people do non-lethal damage in combat because they hold back, not just because they don’t know how.
The superhero genre is distinctly different than other RPG genres, such as mediaeval fantasy or espionage or war. Superheroes constantly have to work around innocent bystanders and pull their punches with street thugs. It’s just part of the genre; your characters will be so powerful that they have to pull their punches with regular humans in order to avoid killing them. You and your gaming group will have to decide how much of that kind of thing is expected in your game world, and how much the police, the government, and the public will be comfortable with heroes who actually kill the bad guys. As always, it’s ultimately up to you, but it is something to think about.