Team AI
When playing through the game in Single Player (or with up to two other human players), you may find that your AI controlled teammates prefer to use the good old foot 'n' fist method to dispatch the legions of enemies. This is fine for the weaker bad guys, but when you need an extra hand, you can simply tap the Left Trigger and have your AI teammates open up on your targeted enemy with their special abilities.

The buck doesn't stop there though, oh no! To add strategy to this re-enforcement tactic, you can pre-select which attack your team mates will do when you tap the Left Trigger. The AI will use the special ability which is assigned to "Right Trigger + A." This means that if you assign an ability like Iron Man's Energy Reroute, and when you call for back-up, Iron Man will buff the team to reduce the amount of energy used by special abilities. This is particularly useful with teammates who can cast a Heal Over Time (HOT) on the whole party.