It wasn't in one issue. It was spread across five Spider-Man and Venom super specials in 1995.
Here's a real quick summary of the whole arc:
Symbiotes use a teleportation kinda thing to come to Earth. Start taking over. Spider-Man, Scarlet Spider and Venom use the machine to goto the Symbiote's own planet and attempt to stop them. After getting overwhelmed, they come back to Earth and see that almost all of the citizens of New York City have been taken over by the Symbiotes (these ones arn't like Venom or Carnage or any of the other Syms already on Earth, they wish to dominate their host. Its explained in these comics that the Venom Symbiote was imprissoned. The other Symbiotes thought it was insane for wishing to become part of its host, rather than take over (so the machine Spidey got the Symbiote from in Secret Wars was actually a prison cell)). Spidey, Scarlet Spider go around for a bit, fighting off the evil Symbiotes. Carnage shows up, and is absorbing all the evil Symbiotes into himself (peeling 'em right off their hosts), making him grow in size. He pretty much becomes a giant, wondering around the city wreaking havok. To finally stop the invasion, Venom uses this psyonic shreik thing (what actually brought the Symbiotes to Earth to begin with) to kill all of the evil Symbiotes off (its a much stronger phsyonic shreik than before) and making Carnage return to his normal size.
http://www.killermovies.com/forums/f77/t419450.html
Goodbye everyone, thanks for the laughs, and spats of furious anger.
Hey to all from this newbie. Got a love for Venom - and everything Symbiote - by way of my son. Would somebody who knows a lot about symbiotes please answer this? I know that the Venom symbiote took an imprint - a copy - of Peter Parker's physical powers when they were bonded as Black Suit Spidey. Did the Symbiote also take a copy of Parker's personality? I'm asking because it seems to me that the Venom personality is different from Brock's in that Venom has kind of a twisted sense of humor. Occured to me that some of Peter Parker's ironic wisecracks are coming through the Venom personality but twisted to reflect Eddie and the Symbiote's "personalities." What do you say?
Alright everybody. I officially got my first fanfic up on my site, give it a read and lemme know what'cha all think.