Because you like Elle Driver in Kill Bill vol. 1
Peter Venkman's "research" projects are designed to get undergraduate students to sleep with him. Though it turns out he can bust ghosts. See them in Ghostbusters.
Villanelle is a hired assassin who loves committing murder as much as she loves dressing up in fancy pink ballgowns. See them in Killing Eve.
Undercover as an average high school student, Kallen Stadtfeld is actually most at ease when the action's fast, furious, and dangerous. See them in Code Geass.
The witty Aku would be an ideal dinner guest, if he weren't a demon. See them in Samurai Jack.
Love Quinn is a trained chef and excellent girlfriend, but she's hiding something dark. And bloody. See them in You.
Benoit Blanc is Sherlock with Southern charm, and a mysterious benefactor. See them in Knives Out.
Rogue's touch is literally deadly, and she's trying to learn from the older mutants how to manager her powers. See them in X-Men Series.
Christine Daae has been secretely taking lessons from a phantom musician. It sounded less creepy in her head. See them in The Phantom of the Opera.