There is a battle of wills that takes place nearly 24/7 in all of us…against ourselves. Everyday we are inundated with do or do-not decisions. What we chose defines how we live our lives, who we are at our core. Consider it part of the human condition.
Now I’m not saying all books have this internal conflict or even delve into it, but a vast majority portray it to some degree. The thief that wants to be noble. The noble that wants to be free. The hunter that doesn’t want to hunt ( 😉 ). Every step they take is defined by pivotal decisions and it is my personal belief that developing and exploring this struggle has the ability to make a story that much better. It makes it real.
No one wants an infallible hero. Unpopular opinion: this is why I’m not a big fan of Superman or Captain America. I’ll take the troubled Dark Knight any day of the week over the boy scout who can do no wrong. Obvious alien particulars aside, he seems more human to me and more importantly, more relatable. 
Lord Byron’s introduction/establishment of the antihero to the literary world pretty much blew the it wide open. People weren’t perfect, why should characters be? Good people do bad things all the time and are still heralded as heroes. Why can’t bad people do good things for a greater purpose (even if that purpose is themselves)? The antihero archetype is everywhere, posing the ultimate antithesis to the classic hero. He doesn’t care about collateral damage unless it suits him, he’s self-motivated, and determined to survive. Remind you of anyone? (*hint*hint* I’m going for yourself)
I once wrote an entire essay relating Lord Byron’s antihero to Riddick (Pitch Black & Chronicles of Riddick). Before everyone freaks out, know this–the teacher freaked too. I was literally given the all clear to write this ridiculous premise simply because she just “had to see how I would pull this off.” And you know what? I did. Because Riddick is the epitome of the Byronic antihero. His internal conflicts swirl around finding a tenuous balance between his own success/survival and those of the few things he cares about outside of himself. His rage fuels him and pushes him to accomplish great things that ultimately benefit the larger whole. But never forget, his ultimate motivation was always himself.
Now this archetype can get twisted into all sorts of deviations including redemption, devolution to absolute villainy, or total change of heart. Truth be told, I’m all for any of these, so long as there is appropriate precedent. There is nothing more insulting to a character than to magically change them #aWizardDidIt. Anyway, I digress.
My main point is that as readers we appreciate being able to relate to the people we read. Make them fallible. Make them learn. Make them grow. And yes, it is completely possible for an antihero to do all of those things and still be an antihero by the end. Maybe they don’t want to be better people. Maybe the world has burned them too many times to forgive. Maybe it’s everyone else that has it wrong and they’re not an antihero at all, but in fact only vilified because they are saying/doing what no one else will.
The struggle is real and it’s there in all of us. Who will you be today? A hero? A bystander? The villain? Or maybe something in between?