Issue: #25
The war between the Avengers and the X-Men has started and it gets through the books of both Avengers titles and X-Men related titles as the battle starts.
Creators: Alan Fine, Axel Alonso, Dan Buckley, Joe Quesada, Scott Hanna, Tom Brevoort, Brian Michael Bendis, Walter Simonson, Daniel Acuña, Lauren Sankovitch, John Denning, Cory Petit, Jason Keith
Characters: Hawkeye, Captain America, Iron Man, Thor, Magneto, Norman Osborn, Spider-Man, Storm, Sunspot, Wolverine, Namor, Colossus, Cyclops, Phoenix Force, Doctor Strange, Spider-Woman, Wonder Man, Vision, Noh-Varr, Thunderbolt Ross
Story arcs: Avengers vs. X-Men