4) John Constantine
From one occult detective to another, John Constantine is also in the business of paranormal investigation. In terms of their characters, Constantine is somewhat the reverse of Hellboy, however. While the latter was able to escape the clutches of Hell and lead a heroic life on Earth, Constantine – in many versions – has his soul damned to spend eternity in Hell upon his death due to his past sins. In the meantime, the Liverpool native is dedicated to saving innocents from the horrors that walk our planet.
Constantine is also another character who isn’t a detective by profession, but his methods and street-level heroics put him on the same level as private eyes rather than fully-fledged superheroes. That said, when called upon, John does have an impressive skillset at his disposal: he’s a master sorcerer with his abilities including teleportation, telekinesis, necromancy and occasionally time travel.
Unusually for comic characters, Constantine ages in real-time (at least in the Vertigo universe, an offshoot of DC). While 35 when his solo series first started, the character is now in his 60s.