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