Because you like Leonard "Bones" McCoy in Star Trek
Toby Cavanaugh has trouble avoiding being manipulated. See them in Pretty Little Liars.
Sylar's victims are found all over the country, many with their brains removed. See them in Heroes.
A premier member of the leather cat-suit club, Selene can chill you with a stony look, or ice you with her ninja moves. See them in Underworld.
Leone Montana is a fearless hitman with a surprisingly sensitive side. See them in Leon: The Professional.
A malevolent dark wizard, Voldemort is so fearsome that he's known primarily as "He Who Must Not Be Named." See them in Harry Potter Series.
Catwoman might be slightly unhinged, but you can't say this feline villainess isn't confident. See them in DC Extended Universe.
Dutiful, composed, and aloof, Sun Bak is the fighting force behind her team of eight "sensates" who are telepathically linked. See them in Sense8.
Abbi Abrams is the ultimate wingwoman because she wants nothing more than to have a good time for its own sake. See them in Broad City.
If anyone can stay optimistic and friendly under harsh alien rule, it's Alyx Vance. See them in Half-Life 2.
As the White House Press Secretary, C. J. Cregg is a master of verbal karate and the best damn basketball player in Ohio Valley history. See them in The West Wing.