I'm looking at some Vertigo comics to read and one interesting character I've been reading on the web about is Hellblazer's John Constantine. From what I gather he fights demons but is condemned to hell no matter what he does? Can someone clarify why his relationship with God is that bad?

The summoning demons and such probably has something to do with it.

Well seeing as how he's used his friends like pawns. That would surely write him a one way ticket.
 
Plus using magic. I remember an issue where he told a bunch of people who abused magic that anyone who uses magic basically is given a one way ticket to hell because they're cheating the system. He used wine as an example so I'll do the same. Imagine the work it takes to make a delicious wine. Seeds must be planted, Grapes must take months to grow, nature has to nurture the grapes, then they have to be picked and squashed into wine. Then the wine has to age in order to become more and more tasty. Well with magic you can skip all of the steps and just conjure up a bottle of wine. No work or effort put into it. You're cheating the world's taxman. Thus using magic is forbidden.

@FIash said:

I'm looking at some Vertigo comics to read and one interesting character I've been reading on the web about is Hellblazer's John Constantine. From what I gather he fights demons but is condemned to hell no matter what he does? Can someone clarify why his relationship with God is that bad?

A couple of thoughts:

First John wouldn't really court a relationship with God because he sees Heaven as overly authoritative and just plain poncy (is that a correct usage I'm a Yank) In his dealings with the archangel Gabriel, Constantine has nothing but derision for the angel and constantly chides him for being out of touch with mortals. John prefers to walk a path between the powers above and below so to speak.

Second, way back in Dangerous Habits (Ennis' definitive arc to many) John tricks the Lords of Hell into a detante over the claim to his soul. Going to war over his soul would put them in a vulnerable position making Hell easy pickings for Heaven, therefore they wait for the opportune moment but keep him alive to prevent war.

Finally, the blood of the demon Nergal pulses through John's veins. Chances are this alone is enough to bar his entrance into Heaven. Not that he would wan't to go there in the first place.