Here is the full list of all 48 Persona 3 Reload achievements. It takes around 60-80 hours to unlock all of the achievements on Windows.
Maxed out all Social Links.
Watched the good ending.
Sealed Nyx.
Fused Messiah.
Unlocked all Social Links.
Awakened all teammates' ultimate Personas.
Invited Elizabeth to your room.
Defeated the Hanged Man.
Nurtured a romance.
Encountered a Dark Zone in Tartarus.
Unlocked a teammate's Combat Characteristic.
Defeated Fortune and Strength.
Discovered and conquered 10 Monad doors.
Maxed out all Social Stats.
Acquired every Twilight Fragment in town.
Defeated the Hermit.
Used all teammates' Theurgy.
Maxed out one Social Stat.
Defeated the Chariot and Justice.
Unlocked access to the remaining Major Arcana.
Triggered a skill change during fusion.
Used a total of 50 Twilight Fragments.
Obtained 10 Major Arcana during Shuffle Time.
Initiated 50 Chance Encounters.
Earned over a total of 50,000 yen from part-time jobs.
Nursed a cat back to full health.
Ordered from a secret menu at the Iwatodai strip mall at night.
Harvested a crop that you grew with a teammate.
Defeated the Hierophant and the Lovers.
Rescued a missing person.
Dealt over 999 damage in a single attack (All-Out Attacks excluded).
Defeated the Reaper.
Spent an evening in the dorm with a teammate.
Performed 50 All-Out Attacks.
Obtained 10 Personas during Shuffle Time.
Defeated the Empress and Emperor.
Accepted an invitation to hang out five times.
Obtained an item from a Persona Conception.
Maxed out one Social Link.
Aced an exam.
Opened 50 treasure chests.
Performed a fusion with three or more Personas.
Defeated the Priestess.
Defeated a rare, golden enemy.
Performed a Shift.
Performed a Dyad Fusion.
Joined the Specialized Extracurricular Execution Squad.
Obtained Orpheus.