Square Enix finally revealed their hotly anticipated Marvel's Avengers game during their E3 2019 presentation and earned some mixed reactions. Part of that was due to some design (and roster) choices of their core Avengers heroes and costumes, but the other part is how lacking in detail on the actual gameplay offerings they were.
For the game meant to close out the Square Enix show with a bang, it was awkward to hear presenters discuss post-release plans and PlayStation exclusivity details instead of showing gameplay and explaining how Marvel's Avengers actually functions, beyond it being single-player and co-op. Even that part was a bit misleading. Thankfully, in some behind-closed-doors presentations on the E3 show floor, we got to see gameplay and chat with devs along with other press.
What the devs were not clear about - and really should have been - is how the co-op works. The main story campaign of the Avengers video game releasing in 2020 from developers Crystal Dynamics and Eidos Montreal is not multiplayer in any way. It's like Spider-Man PS4 that way.
Marvel's Avengers Campaign is NOT Actually Co-op
The main campaign teased in the Avengers game trailer and the gameplay we saw is heavily scripted, loaded with quick-time events, and very cinematic so it isn't designed to work with multiple players. Instead, as players play through the story of Marvel's Avengers, side missions are unlocked that can be played cooperatively. In these missions, players can choose which characters they wish to play and can level that hero up.
These side missions apparently have stories of their own, but given how secondary they are to the main game it's unclear how much depth these will have, or if they'll be more generic action arenas, wave-based horde modes, etc.
The side missions can be played solo as well.
Is Marvel's Avengers Online Only?
To play Marvel's Avengers cooperatively, players must be connected to their online service and can only play online. Local splitscreen play is not supported.
The main story campaign and playing the side mission solo can be player entirely offline.
How many player co-op can Play Marvel's Avengers?
The cooperative side missions in Marvel's Avengers can be played with 2-4 players, online only.
Again, players can also play solo and offline.
Source: Crystal Dynamics