This is a list of superheroes that have been involved in some way with John Constantine. 'Minor' means that they have only played a small or single role in his stories, not that they are not important in of themselves.
After seeing his parents murdered, billionaire Bruce Wayne dedicated his life to becoming the greatest detective in the history of mankind. He has encountered Constantine on just a couple of occasions - first during the Crisis on Infinite Earths, when they met by chance in a street (Swamp Thing volume 2 issue 44 and then when Constantine sought his help to track down a deranged Swamp Thing (The Search for Swamp Thing issue one. Batman dislikes Constantine's attitude, but will begrudgingly work with him if he has to.
First appearance: Detective Comics issue 27
The last son of Krypton, Kal-El was sent to Earth by his parents to escape the destruction of their planet. There, he was raised by a kindly Kansas couple and became Superman, the greatest superhero of them all. Constantine sought his help to track down a deranged Swamp Thing (The Search for Swamp Thing issue two. Constantine's lack of interest in helping people in trouble unless it benefits him puts Superman's back up somewhat.
First appearance: Action Comics issue 1