Because you like Rupert Giles in Buffy the Vampire Slayer
Dolores Umbridge keeps her villainy hidden (albeit poorly) behind a sheen of sugary pink politeness. See them in Harry Potter Series.
The brilliant Mona Vanderwaal is proof that undergoing an "extreme makeover" isn't always a good thing. See them in Pretty Little Liars.
Ellen Ripley defines the word "badass." When she's not leading her crew on an interstellar voyage, she's slaying terrifying creatures. See them in Alien.
Jean-Baptiste Grenouille may have a phenomenal sense of smell, but he has a weak sense of morality. See them in Perfume: The Story of a Murderer.
Sookie Stackhouse is a waitress who can read minds and break hearts. See them in True Blood.
Sephiroth wants nothing more than to seize the power of the Lifestream in order to become a god. See them in Final Fantasy Series.
Frank Reynolds is too gross even for the prostitutes he hires. See them in It's Always Sunny in Philadelphia .
A monstrous pirate captain, Davy Jones is quite literally heartless. See them in Pirates of the Caribbean: the Curse of the Black Pearl.
Juliet Capulet falls head over heels for her rival family's resident sweet talker, Romeo. See them in Romeo & Juliet.
Wanting more out of life, Pam Beesly has a job she isn't crazy about and is engaged to a guy she's not sure is "The One." See them in The Office.
Mrs. Lovett is the proud purveyor of the worst, and most grisly, pies in London. See them in Sweeney Todd: The Demon Barber of Fleet Street.