Here is the full list of all 31 Final Fantasy XIII-2 achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Dealt 99,999 damage with a single attack.
Responded swiftly to the appearance of enemies.
Befriended a most unfriendly monster.
Defeated a powerful enemy on equal terms.
Witnessed every possible Paradox Ending.
Completed every fragment category.
Followed the story to its conclusion.
Obtained the highest possible result in the battle to determine the fate of the world.
Turned your back on empty dreams and joined the battle to save mankind.
Defeated a powerful enemy with perfect execution.
Fought a significant number of battles without using the "Retry" option.
Prepared to face a test of your determination in the rift where hidden truths slumber.
Defeated a powerful enemy with valiant skill.
Acknowledged the threat facing the world, and decided to fight back.
Performed a significant number of preemptive strikes.
Completed an entire fragment category.
Went the distance on chocobo-back.
Defeated every worthy opponent.
Staggered a significant number of enemies.
Defeated an army's worth of enemies.
Visited the place where the saviors of the past dream in crystal.
Spent a fortune at shops.
Fully developed all abilities.
Visited the place where clues to the future lie waiting to be discovered.
Accepted a new fate in a world where everything has changed.
Left behind a normal life, and began a journey through time.
Obtained five Cinematic Bonus rewards.
Amassed a fortune in casino coins.
Defeated a powerful enemy with graceful poise.
Successfully used Feral Link abilities a significant number of times.
Performed a multitude of paradigm shifts.