Because you like Raistlin Majere in Dragons of Autumn Twilight
Veronica Sawyer thinks that if you were happy every day of your life you wouldn't be a human being, you'd be a game-show host. See them in Heathers.
Orphan Bruce Wayne has a tortured soul, but he's trying his best to weed out corruption. See them in DC Extended Universe.
The adventurous daughter of Port Royal's governor, Elizabeth Swann would rather conspire with pirates than sit pretty in her corset. See them in Pirates of the Caribbean: the Curse of the Black Pearl.
A superpowered test subject, Scarlet Witch can manipulate other people's thoughts and force them to confront their worst fears. See them in Marvel Cinematic Universe.
Hiccup Haddock III may be the only Viking nerd in recorded history. See them in How to Train Your Dragon.
John Watson is haunted by his past (who isn't) but he's starting to branch out with some help from a world class detective. See them in Sherlock.
His murderous megalomania aside, Loki is quite charming. Just don't mention his strapping older brother; he's a tad jealous. See them in Marvel Cinematic Universe.
Smart and sensitive Sam Winchester tried to escape the family business, but ghosts have a way of haunting you. See them in Supernatural.
When the Sorting Hat touched Draco Malfoy's head, it placed him in Slytherin, a house that has turned out more dark wizards than any other. See them in Harry Potter Series.
L is enigmatic, child-like, and one of the smartest people in the world. See them in Death Note.
Severus Snape is a misanthropic potions teacher with a vindictive streak. See them in Harry Potter Series.