Here is the full list of all 53 Persona 5 Royal achievements. It takes around 80-100 hours to unlock all of the achievements on Windows.
Unlocked all achievements.
Watched the ending.
Completed every Palace.
Conquered the Reaper.
Evolved a party member's Persona.
Completed Mementos.
Completed the cruise ship Palace.
Completed the casino Palace.
Completely changed the cognition of Mementos.
Maxed out all social stats.
Scored the highest on your exams.
Completed the spaceport Palace.
Ordered from the special menu at the maid café.
Scored a prize in the crane game.
Completed the pyramid Palace.
Maxed out one of your Confidants.
Entered a special relationship.
Performed a Gallows execution.
Customized a gun.
Completed the bank Palace.
Attended the jazz club.
Passed time at the fishing pond.
Visited a temple.
Performed an execution during a Fusion Alarm.
Performed a Showtime attack.
Played a game of darts.
Performed a Group Guillotine execution.
Used Incense on a Persona in Lockdown.
Played a game of billiards.
Sold old clothing at Furugi no Neuchi.
Completed the museum Palace.
Performed an Electric Chair execution.
Encountered a deviation in Mementos.
Obtained a Treasure Demon.
Couldn't take the heat in the bathhouse.
Cleaned up in Leblanc.
Went to a hangout spot with someone.
Traded in stamps while in Mementos.
Traded in flowers while in Mementos.
Obtained a Skill Accessory from a Palace ruler.
Completed a Mementos request.
Won the lottery.
Established your own squad of thieves.
Completed the castle Palace.
Worked a part-time job.
Defeated enemies via Disaster Shadow explosion.
Triggered a Technical.
Used the grappling hook.
Performed a Guillotine execution.
Performed a Baton Pass.
Scored a hit at the batting cages.
Obtained a Persona through negotiation.
Obtained Arsène.