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