The answer to this question is completely dependent on the reader. I've had readers say that McCandless was a romantic, an adventurer, or a naturalist. I've also had readers tell me that McCandless was an ignoramus, a loner, a fool, or an anti-establishment rebel.
Gallien asked whether he had a hunting license. “Hell, no,” Alex scoffed. “How I feed myself is none of the government’s business. Fuck their stupid rules.”
I believe that each one of those could be effectively supported with evidence from the text. McCandless is no doubt okay with being alone. Much of Krakauer's account clearly shows that McCandless preferred being by himself in wild locations like the backwoods of Alaska or the deserts of the American southwest. McCandless prefers solitude over company; however, McCandless isn't averse to being around people. He is completely capable of carrying himself in conversation and being emotionally fed from good company. It's why he continually returns to Westerberg and spends so much time with Franz.
I suppose if had to pick a single term that described McCandless, I would pick "individualist." That term encompasses the positive and negative aspects of McCandless. He does what he wants to do when he wants to do it. He was a living example of carpe diem. He listened to other people and acknowledged their advice, but when it came down to it, McCandless was going to do what he thought was in his best interest. McCandless was like this his entire life, and even his third grade teacher recognized this fact.
His teacher pulled us aside and told us that "Chris marches to a different drummer."