Gone is the open-world, X-Men Legends action-RPG style gameplay of the first title. Here, things play out more like your standard 3D beat-'em-up, with co-op on all of the time. Heroes are assigned automatically by stage and storyline, and if you're not playing with a friend, then the AI takes over. At the very least, the always-on co-op helps to keep the banter and sound bites fresh. The game may also see fit to switch pairs of players during certain points in the mission (such as in The Swamp, where you can control Katara/Momo and Aang/Sokka teams.). At the end of each level is a boss, which can then be unlocked to fight in the game's Arena Mode.
Just because the game's switched to a beat-'em-up core, however, doesn't mean that there aren't things to break up the action. Co-op puzzles abound, as well as obstacles that require the use of a certain type of bender or warrior to get past. Aang can blow obstacles out of the way, for example, and Sokka can cut things with his boomerang. A bit of stealth has also been added, such as when Aang and Sokka sneak past guards (tiptoeing and hiding inside barrels) into the Bei Fong estate to speak to Toph.