2) The Spectre
Another Constantine character we want to see more of is Jim Corrigan. On that show, Corrigan appeared as a regular ol’ detective and ally of Constantine’s. What interests fans most about the character, though, is that he becomes the supernatural superhero The Spectre in the comics.
After being killed, Corrigan’s soul was sent back to Earth to rid the world of evil. Constantine was very clearly setting up the character’s death and resurrection but it never got to fulfil this as it was taken off the air after only 13 episodes. The character is practically screaming out to be further explored then in another Arrowverse show. The best fit for The Spectre would probably be Legends as, yet again, he holds a Justice Society membership card.