You might like to review Chapter 11, which gives us important information about Chris's upbringing and what he was like as a child and how he developed into the young man he became. There are lots of quotes from this chapter that could be used to answer your question, but you might like to think about this one, that is rather balanced in the way that it presents Chris:
McCandless's personality was puzzling in its complexity. He was intensely private but could be convivial and gregarious in the extreme. And despire his overdeveloped social conscience, he was no tight-lipped, perpetually grim do-gooder who frowned on fun. To the contrary, he enjoyed tipping a glass now and then and was an incorrigible ham.
What draws my attention to this statement is the way that it shows how the character of Chris McCandless defies easily categorisation. Krakauer presents us with stereotypes that Chris is shown not to fit, pointing towards the "complexity" of his character and the dangers of writing off his death with answers that are too easy and do not really penetrate the depths of his character.