Because you like Amy Pond in Doctor Who
Cinder has been beaten down by the world, but she's learning that her cyborg abilities are pretty helpful. See them in Cinder .
Ellie is more world-weary than most 14-year-olds. You would be too if your world was infested with zombies. See them in The Last of Us.
Rue Bennett has been overprescribed and under-supervised her entire life. See them in Euphoria.
A great galactic bounty hunter, Samus Aran is not as good at expressing emotions. See them in Metroid.
Kenzo Tenma would have never guessed that ten-year-old he saved would later become a deadly serial killer intent on "thanking" him. See them in Monster (TV Show).
Formerly a "sweater-set-wearing, mojito-drinking sorority girl", Paige Collins is now a successful sculptor with slight memory loss. See them in The Vow.
The vampire that killed Zero Kiryu's family also infected him, and he starts to crave blood, much to his horror. See them in Vampire Knight.
When push comes to shove, the usually overly cautious Luigi has the heart of a hero. See them in Super Mario Bros..
Rose Hathaway is a reckless, rebellious smartass who's training to be a royal vampire guardian. See them in Vampire Academy.
When dealing with a half-demon partner and a world of violence, Kagome Higurashi has plenty of chances for her true courage to shine. See them in Inuyasha.