Because you like John Doe in Se7en
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.
A no-nonsense pro, Agent K has dedicated his whole life to his job. See them in Men in Black.
How lucky are we that Arthur Curry, the King of Atlantis, hasn't taken over the surface world? Very! See them in DC Extended Universe.
A gifted detective, Rust Cohle is as dark and twisty as any murderer he chases. See them in True Detective Season 1.
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.
A monstrous pirate captain, Davy Jones is quite literally heartless. See them in Pirates of the Caribbean: the Curse of the Black Pearl.
Leone Montana is a fearless hitman with a surprisingly sensitive side. See them in Leon: The Professional.
Beware! Anton Chigurh carries a coin with him, which he forces his victims to flip to decide whether they will live or die. See them in No Country for Old Men.
With those dearest to him dead and no one to trust, Max Rockatansky is a slightly hysterical man alone on the run in a post-apocalyptic world. See them in Mad Max: Fury Road.
Bob Parr is an ex-superhero now focused on being a dad, but he misses the action. See them in The Incredibles.
Hunting ghosts is both a job and a passion for Abby Yates. See them in Ghostbusters (2016).