Because you like Joanna Kramer in Kramer vs. Kramer
Darcy Lewis is a razor-sharp scientist studying things that science can't explain. See them in Thor.
The fearless bodyguard of Rick Flag, Katana will ruthlessly kill her enemies, trapping their souls in her sword. See them in DC Extended Universe.
Hank McCoy is a quintessential nerdy scientist but with a few rather unconventional physical attributes. See them in X-Men Series.
If it means fulfilling her ambitions, Satsuki Kiryuin will show neither shame nor hesitation. See them in Kill la Kill.
Born and raised in the darkness, Bane is determined to have the city totally under his control so that he can demolish it. See them in DC Extended Universe.
Wanderer is a Soul, a parasite sent into a host to take over their body, extracting information from them and colonizing their species. See them in The Host.
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.
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.
Jack Bauer is a terrorist fighter who is scared of nothing and no one. The clock is ticking! See them in 24.