More than anything else, invulnerability is the centerpiece of the superhero genre.
There are characters who can fight other people, characters who can beat opponents, characters who can shoot opponents, characters who can talk others down, plan things around them, characters who can present lethal force and characters who can present nonlethal force, but when there is a character – a heroic character – who walks through what the enemies do, unharmed, when they do not need to fear the people who can do all the others, that is the genesis of the story space that goes towards superheroes.
And what’s more, that invulnerability creates a new moral impetus. Suddenly, when a character is safe, when a character is beyond harm, there becomes a question of what to do with that personal safety? How many stories are about characters who are functionally immune to harm who idle around and boredly don’t do things?
This is one of those things Luke Cage does that I really love. There’s one scene, just the first scene where we’re shown his invulnerability, in action, in practice, and watching the physics-defying nonsense of two people trying to punch and hurt Luke and the action slows and stops and suddenly you just revel in the moment of our protagonist being utterly unhurt.