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