Atlas is a boss in Final Fantasy XIII-2. The player can fight it in its weakened state after examining the mysterious device that appears in the Bresha Ruins, or at its full power; the latter of these two possible battles is much harder. Fighting Atlas in his full power form is required to complete a paradox ending. Defeating Atlas's weakened form with a 5-star battle rating earns the player the Scarlet Medal achievement/trophy.
Cinematic Actions are presented during the course of this battle in the main storyline
Only two of the three primary elements of paradigm tactics are likely to be available to Serah and Noel for this battle. Commando and Ravager may be used, but instead of the Medic role, the player will likely have chosen an extra ATB segment as their first bonus. This forces the player to rely on potions or a Cait Sith Medic, and/or a Pulse Knight Sentinel, to defeat this boss. It is quite possible to achieve a 5-star rating.
Tri-disaster (RAV/RAV/RAV) - This paradigm will be used to stagger Atlas as quickly as possible by filling the chain gauge.
Cerberus (COM/COM/COM) - This paradigm will be used to quickly take down Atlas once it is staggered and also increase the amount of time Atlas stays staggered, by attacking at the beginning of the battle.
Tortoise (SEN/SEN/SEN) - The defensive paradigm that the game suggests for Gogmagog's first and second forms. With impeccable timing, the player can see Atlas's attacks coming, and will spend no more than a couple of segments in Tortoise, giving time to use Potions to heal; if this proves to be insufficient time for the Sentinels to do their work, spend more time. If potions prove inadequate, Cait Sith must replace either the RAV, COM, or SEN tamed creature.
Just because Atlas is at a weak state, it should not be underestimated. It will attack with powerful punches and a damaging roar, capable of inflicting Curse on the party and also wounding it. As the player may not have unlocked the Medic role for everyone yet, any Paradigm with Medics will do, but having more is always safer.
The party should start the chain gauge in the Cerberus Paradigm as soon as the battle begins and quickly shift into Tri-disaster to fill Atlas's chain gauge. The boss will fall over unable to attack once staggered, so the party should immediately shift into Cerberus and deplete its HP. With Atlas's HP taken care of, a Cinematic Action will begin. Executing the on-screen prompts clears the battle and defeats Atlas.
The player should wait until Serah and Noel have around 3500 HP each before attempting to beat the boss at its full strength. A recommended Paradigm Pack would consist of an efficient Medic, a good Commando (Early Peakers such as Dragoon and Orion work well), and a Sentinel with high HP.
The following Paradigms are recommended:
Relentless Assault (RAV/RAV/COM)
Tireless Charge (COM/COM/MED) or Diversity (COM/RAV/MED)
The Bloodguard accessories acquired from chocobo racing also work well here, as well as a good supply of Wound Potions. The battle consist of a regular pattern. Relentless Assault should be used to bring up the enemy's chain gauge while it is not attacking, and Cerberus should be used when it is staggered.
Whenever Atlas attacks, the party should immediately switch to Tortoise to tank the damage, and then switch to Tireless Charge/Diversity to heal while keeping up the chain gauge. Whenever any party member has HP Critical health, they should immediately switch to Salvation to heal them, and make sure to use a Phoenix Down rather than Raise to revive party members as it is more effective and heals cumulative wound damage. It is also a good idea to quickly switch to Salvation and back to Tortoise in between the enemy's successive punching attacks to prevent too much damage.
If the player is having difficulty, a sixth Paradigm can be used, Safe Subversion (SAB/SAB/MED), to try and inflict Deshell, Deprotect and even Imperil, despite their low success rate, to improve damage potential and quicken the stagger.