Final answer:
Nora is the character who significantly contributes to changing Mr. Rybar's viewpoint, as she helps initiate a moment of self-realization and transformation in the narrative through a commitment to change.
Step-by-step explanation:
In addressing the question of who helps most in changing Mr. Rybar's viewpoint, it is implied through the given excerpt that Nora plays a significant role. The transformation of a character's perspective within a narrative generally requires a deep commitment to changing their thinking and behaviors. The excerpt indicates a moment of realization or pivot in the character's development, hinting at a personal change in belief and a reevaluation of what is possible, spurred by interactions with Nora. This is not uncommon in literature where character transformations often underpin pivotal plot developments.