Hey Superhero Writers Does Your MC Grow?

The main reason 2001 doesn't have much of a character arc is that it has three acts with no overlapping characters. The protagonist, in some ways, is the black box. The Red Violin's titular character works similarly, but each segment develops a human character as well.

However, I think that the idea of character growth in general masks a different issue, which is that character development in a story is often not "growth" or change, but the character being revealed by the course of the story. This is functionally very similar, because audience's impression of the character alters over time, but the character herself isn't changing but being revealed to be something greater and different than at earlier points in the story.

I will never forget my first impression of Indiana Jones from the first five minutes of Raiders. He appears to be a callous and unwise criminal, blindly leading his employees into danger. In those moments it appeared that he would never be likeable. From there he graduates to talented screw-up, then womanizer, tough guy, respected friend, romantic partner and finally the bravest man on earth. But Jones never changes, we just see him in different circumstances.

Iain Banks' Use of Weapons has an entire plot structure that functions similarly, counting down to an intersection of the protagonist's many parts to finally reveal him in full.

 

The superhero MC does grow and change, but not in the traditional sense. As a superhero, they're probably a loner. He/She is not gonna change at the drop of a hat. Batman is a persona, he's not an actual person. Bruce Wayne changes with each new development, but Batman is only a persona he takes on when he dons the cape and cowl.
Superheroes are complicated to design and develop because there are so many facets to work with. You have the actual person, and then the person they portray themselves as when they are doing hero things. It's not as simple as "The hero's values don't grow and change", they do. It's not gonna be spelled out for you that the hero came out of the experience differently than he went in, because the hero is not real. The person behind the mask is the one changing, the hero is a facade.