In Katherine Paterson's novel, Bridge to Terabithia, I think there are several conflicts, some of which do not become as important until the later part of the story.
However, the conflict that seems to generate and move the plot along, in my opinion, is man vs. society.
Jess has dreams of impressing his school mates (which is destroyed when Leslie joins the school and beats everyone else).
One time last year Jesse had won. Not just the first heat but the whole shebang. Only once. but it had put into his mouth a taste fr winning...For the rest of that day, and until after lunch on the next, he had been "the fastest kind in the third, fourth and fifth grades," and he only a fourth grader.
This sense Jess has to beat all the other boys defines his sense of success for himself, but it is his desire to take on all of his peers that drives him.
Leslie struggles with "society" as well. Her parents, in order to live a more meaningful life, sold their home in Arlington and moved out to the farm: they actually meant to farm it, and as Jess sees it, Leslie has to pay the price by being forced to leave friends and school to enter a world of strangers.
Jess and Leslie form a strong bond, creating an imaginary world where they are in charge. This may be in response primarily because of the needs of family that are not met, a feeling that they don't have control of their lives at home.
Because both youngsters are in need of attention—support and understanding from their parents—I have categorized this as man vs society. If Leslie did not get along with her mother, or Jess, his mother, I would characterize these examples as man vs. man. However, because the children's needs extend from a sense of dissatisfaction at home, for different reasons—for the most part—it is as if they are at odds with society in general.
When tragedy strikes in their midst, this conflict will continue until it is resolved by all those involved.