Mattie

Yep.

They went back to the original text and restored the narrative center of gravity to where it actually belonged, which was the character of Mattie Ross.

Hailee Steinfeld's character.

Yeah.

Which is?

The book is actually incredibly funny.

Mattie Ross is written as a bloody-minded, grudge-nursing, hyper-articulate comic creation.

He argued that focusing only on the grimness loses some of the original's brilliant humor.

The ghosts of Christmas keep prodding Scrooge out of his inveterate miserliness.

And Mattie Ross, who is actually a flat arc protagonist, keeps dragging compromising lawman Rooster Cogburn back onto the road to justice.

Now, the impact character may or may not be actively or even consciously trying to get the protagonist to see that truth.

Although sometimes the impact character may represent a dedicated mentor character, this is not always the case.