Though McCandless was a pretty smart kid, evidenced by his success in school and perhaps even more so by his ability to get along with people and to accomplish just about everything he put his mind to, he showed quite a lot of prideful ignorance in his journey out into the Alaskan "wilderness," as he was woefully underprepared for the adventure. His lack of interest in reading about or listening to all the people who tried to tell him that there were things he ought to be doing before heading out demonstrate the fact that he was inordinately prideful about his ability to survive in this environment.
I don't believe that McCandless was guilty of hubris in regards to his trip into the wilderness (perhaps he was in regards to his disdain for his parents' lifestyle). My opinion is based wholly on Jon Krakauer's account of McCandless's "adventure." While Chris acted foolishly in some cases and appeared to be unprepared, that seems to have been his goal--he wanted to challenge himself and see if he could survive off the land. He seems to have known himself well enough to have realized that if he took too much with him or prepared too completelythat he might not have the genuine experience that he was seeking. He desired to have a Thoreau-adventure and sought to be as authentic as possible. If he were guilty of hubris, I believe that he would have gone into the situation thinking that he would survive no matter what. Krakauer seems to portray him as someone who went into the situation knowing that he might not survive but at least he tried to live his dream.
Chris's decision to venture into the wilds of Alaska could certainly be considered foolhardy and arrogant. Despite the fact that he had some experience in the wilderness and has proven himself successful in such adventures previously, Chris has little intimate knowledge of the area into which he was journeying and very limited knowledge of the flora and fauna he would encounter. His supplied were extremely limited and his equipment very minimal. Although his idealism and focus on living beyond materialism and consumerism are certainly noble and admirable, his lack of planning and preparation are not. Was Chris guilt of hubris? That's a great question that each of us must ask of ourselves, but there is certainly evidence for either answer.
Hubris means to be overly confident or arrogant. Chris McCandless demonstrated this when he entered the wild with few supplies and a sense that he could survive in the wild. He chose to leave his map on the dashboard of the man who had driven him to the entrance point of the Alaskan park. If he had the map he would have known that there was a bridge that would allow him to cross the river so he could make it back to civilization.
In the past he had almost died in the desert. He had taken off relatively unprepared and been lost. It was another example of his feeling hubris-tic nature. Had he not been that way he would probably still be alive.