Because you like The Wicked Witch of the West in The Wizard of Oz
With an abundant supply of alcohol, nice restaurants, and free will, Crowley is a demon who is thoroughly enjoying his time on Earth. See them in Good Omens: The Nice and Accurate Prophecies of Agnes Nutter, Witch.
Kind and friendly, Rinoa Heartilly is nonetheless an effective freedom fighter. See them in Final Fantasy Series.
Anastasia Steele's new boyfriend Christian might as well come with a warning label that reads "Beware: Severe Issues That Might Warrant a Trip to Dr. Phil." See them in Fifty Shades of Grey.
Bucky Barnes used to be a good-hearted American soldier. Now he's the cold-hearted Winter Soldier. See them in Marvel Cinematic Universe.
Donna is boisterous and spunky traveller of the TARDIS, exploring worlds beyond the simple mundane enterprises of Earth. See them in Doctor Who.
Lying is the most fun a girl like Alice can have without taking her clothes off. See them in Closer.
Nicholas Angel is super-dedicated to his job as a police officer. Maybe a little too dedicated. See them in Hot Fuzz.
CIA operative Carrie Mathison is on a self-assigned mission to follow a lead, whether it be the truth or just her delusions playing tricks. See them in Homeland.
A Berlin-based locksmith by day, Wolfgang Bogdanow is a world-class thief by night. He can also see out of other people's eyes, but that's a different issue. See them in Sense8.
Rick Sanchez is a gruff, alcoholic mad scientist, with the emphasis on "mad." See them in Rick and Morty.
Mac is a karate-chopping, beer-chugging schemer. See them in It's Always Sunny in Philadelphia .