Oh, a great deal is wrong with Eddie. There's the obvious post-traumatic psychic scarring that comes from fighting a god... and then there's the alien life-form attached to his central nervous system that has infuriatingly placed him into a coma-like stasis. Aside from that? To answer your actual question... he has quite a lot of cancer. 
Appearing in 1st story
Featured Characters:
- Venom (Eddie Brock) (Main story and flashback)
Supporting Characters:
Antagonists:
- Carl Brock (Only in flashback)
Other Characters:
- Chip (Mentioned)
- Spider-Man (Peter Parker) (Mentioned)
- Mr. Belvedere (Only in flashback)
- Miss Lewis' son (Death) (Only in flashback)
- Mary Brock (Mentioned)
- God (Yahweh) (Invoked) (Only in flashback)
- SFPD (Main story and flashback)
- Flash Thompson (Mentioned) (Deceased)
- Grendel Symbiote
- Project Oversight
- The Maker (Reed Richards)
- Unnamed agents
- Jamie Brock (Mentioned)
- Dylan's mother (Mentioned)
Races and Species:
- Humans (Main story and flashback)
- Symbiotes
- Dogs (Mentioned)
- Cats (Only in flashback)
- Alien Gods (Illusion or holographic simulation)
Locations:
- Prime Marvel Universe (Main story and flashback)
- Earth (Main story and flashback)
- United States of America (Main story and flashback)
- California (Main story and flashback)
- San Francisco (Main story and flashback)
- Tenderloin (Main story and flashback)
- Todd's Diner (First appearance)
- 714 Jenkins Avenue (Carl Brock's house) (Only in flashback)
- Nob Hill
- San Francisco Memorial Hospital
- Tenderloin (Main story and flashback)
- San Francisco (Main story and flashback)
- California (Main story and flashback)
- United States of America (Main story and flashback)
- Earth (Main story and flashback)
- Ultimate Universe (Referenced)
Events:
- Oversight (Referenced)
Synopsis for 1st story
Sitting in a diner booth, Eddie Brock marvels at the existence of his newfound younger half-brother Dylan... before thinking he'd rather have a rematch with the Grendel than sit through Dylan's barrage of annoying questions. The waiter approaches and tells Eddie that they don't allow animals inside the establishment, indicating the Venom symbiote - which is again in the form of a dog. Eddie tells the waiter that "Randy" is a service animal who helps him with his PTSD, and the waiter mistakenly assumes Eddie is a soldier and thanks him for his service. As the waiter leaves, Dylan scolds Eddie for pretending to be a soldier, but Eddie interrupts and asks why Dylan asked him to kill their father. Rather than replying, Dylan asks Eddie why Carl Brock hates him so much. Eddie states that when he was a teenager he'd stolen his father's car to get drunk with some friends, and while trying to sneak the car home had accidentally run over and killed his neighbor's young son. Dylan starts to tell Eddie that he doesn't think that makes him a monster, but as he reaches out the symbiote stabs the table between them with a tendril. Eddie tells Dylan not to touch him, then says that Carl tried to use his power and privilege as a wealthy and respected member of the community to get the incident covered up. However, Eddie had refused to plead not guilty, insisting that he deserved to be punished for killing an innocent child. Asking the police chief to give him some time alone with his son, Carl stated that this incident could ruin his reputation and status, and proceeded to viciously beat Eddie until he agreed to plead innocent. Despite Eddie being let off without even a mark on his record, Carl nearly bankrupted himself paying off the lawyer, judge, hospital, and the boy's family to cover the incident up; and Eddie had never forgiven himself and developed an obsession with protecting the innocent.
As they walk down the rainy nighttime street, Eddie asks Dylan to tell him why he wants their father dead. Dylan admits he spoke out of anger and doesn't really want Carl to die, just for him to stop hurting him. Eddie takes stock of Dylan's black eye and broken arm, asking if Carl did that; and Dylan states that when he gets angry he loses control and turns into a monster. Eddie assures Dylan he'll take care of it before asking if he has a place to stay, Dylan remarking he thought he'd stay with Eddie. Eddie shows him to the mattress in an alley where Dylan had found him, to his half-brother's dismay. When Eddie begins coughing, Dylan asks if he's alright; but Eddie brushes off the question and asks if he's been in touch with his Aunt Mary. Dylan remarks he doesn't have an aunt, causing Eddie to angrily berate the symbiote for messing with his memories. Sporting an ominous expression, Dylan asks if he's sure the symbiote is responsible; saying that maybe Eddie is infected as he suddenly transforms into Knull. Recoiling in horror, Eddie protests that he and the symbiote killed Knull, but the dark elder god sneers that he cannot die and that he is coming to exact his revenge. Eddie transforms into Venom and lashes out, declaring that God dies tonight as he transforms his arm into a blade. Knull cringes and pleads for Eddie to stop, causing him to come to his senses and realize the dark god was a hallucination and that he was about to kill Dylan. Confused and horrified, Eddie suddenly doubles over and vomits blood, telling Dylan to stay away and that he can't help him before passing out.
Later, Dylan sits in a hospital waiting room when two men in suits approach and ask if he was with Eddie Brock, saying he needs to come with them. Dylan tells them that he's Eddie's half-brother and asks if he's in trouble, but while he's talking one of the men stabs him in the shoulder with a syringe and extracts a sample of blood. Confused, Dylan demands to know what's going on and what's wrong with Eddie. Standing at Eddie's bedside, The Maker replies that a lot is wrong with Eddie: the PTSD from fighting an alien god, his bond to the symbiote - which has cocooned him and placed him in a comatose state, and the sudden resurgence of his cancer with a vengeance.
Solicit Synopsis
• Eddie Brock takes a walk down memory lane and revisits San Francisco for the first time in years.
• The homecoming is anything but pleasant, though, as he comes face-to-face with his estranged father and a little brother he never knew he had…
• This while the Venom symbiote remains silenced, perhaps forever, leaving Eddie to struggle by himself…Trivia
- Todd's Diner is a reference to Todd McFarlane, the artist who first drew Eddie Brock as Venom; while Eddie calling the symbiote Randy is a reference to Randy Schueller, the person who originally came up with the concept for Spider-Man's black suit.