Friday August 22, 2014 at 1:13am PDT (check back - new cheats added daily)
There are three possible endings in the game in story mode: Regular ending (Magneto's Victory): Defeat Bastion with Magneto. Alternate ending (Phoenix's Victory): Lose the Magneto vs. Bastion fight and you will go to the Phoenix vs. Bastion fight. Defeat Bastion with Phoenix. Secret Ending (Fury of Dark Phoenix): Get a "Perfect" victory in the Phoenix vs. Bastion fight. This will also unlock Dark Phoenix as a playable character.