Jon Krakauer explicitly states in the introduction that while he attempted to tell the story as objectively as possible, authorial bias creeped in due to his own empathy for Chris. Throughout, Chris's mistakes are contrasted with his noble goals, and Krakauer even contrasts an event from his own life. The most obvious example of pathos is the relationship between Chris and his parents; it is clear from the subtext that Chris loved his parents, but was unable to reconcile his love with his own ideals. In one anecdote, this love is clearly shown:
[Chris] got real emotional. He was almost crying, fighting back the tears, telling Dad that even though they'd had their differences over the years, he was grateful for all the things Dad had done for him. Chris said how much he respected Dad for starting from nothing, working his way through college, busting his ass to support eight kids.
(Krakauer, Into the Wild, Amazon.com)
Along with the occasional interjection from other characters about how Chris should contact his family, this shows both Chris's alienation from society and his determination to follow his personal ideals. Chris refused to compromise, even when it was clear that he understood and appreciated his parents for their hard work and sacrifice. By appealing to the connection that most people feel with their own parents, Krakauer adds a subtle layer of empathy to Chris and his situation, even if it is moderation by Chris's own deliberate desire to cut his parents out of his life.