Because you like Tulip O'Hare in Preacher
Kara "Starbuck" Thrace will beat you in cards, drink you under the table, then fly circles around you in her fighter plane. See them in Battlestar Galactica.
Ultron is security software turned evil mastermind. See them in Marvel Cinematic Universe.
They say they saved Adam Jensen by turning him into a cyborg, but he's not sure saved is the right word. See them in Deus Ex Series.
Working as a captain in the American Expeditionary Forces and a spy for British Intelligence, Steve Trevor wants to end World War I once and for all. See them in DC Extended Universe.
Count Olaf is a traveling actor, except he can't act and his homicidal tendencies make finding work pretty difficult. See them in Lemony Snicket's A Series of Unfortunate Events.
Keeping your cool is just as useful in the underworld as in war, and Michael Corleone is stone-cold. See them in The Godfather.
Point the fun-loving Pippin Took towards second breakfast, and he's one happy hobbit. See them in The Lord of the Rings.
Catwoman might be slightly unhinged, but you can't say this feline villainess isn't confident. See them in DC Extended Universe.
Nandor is a relentless vampire who never admits he's wrong, loves glitter, and can't use a tablet. See them in What We Do In The Shadows.
Jane Smith is a stone-cold killer, but you would never know it from looking at her. See them in Mr. & Mrs. Smith.
Izzie Stevens is a model-turned-med student who can do it all, even if people underestimate her. See them in Grey's Anatomy.