Fellow Screenwriters, how do you make a Protagonist who DOESN'T CHANGE interesting?

Hey, people!

How would you make the readers empathize/sympathize with a character who remains the same?

Would it be better if I have an Antagonist who doesn't change, but changes the Protagonist instead of having the protagonist be like that?

Could differences between his beliefs and his actions be a good way to do it? Is that enough?