Here is the full list of all 19 Doki Doki Literature Club Plus! achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Achieve 100% data collection.
Listen to a lot of what Monika has to say.
Spend 20 minutes listening to music on the desktop.
Draw boxes on the desktop.
Choose not to quit DDLC.
Finish all of the Side Stories.
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Review Paula's project plan.
Write a poem in 20 seconds or less.
Find Dan's special note.
Delete Monika twice while getting deleted zero times.
Write a perfect poem for Sayori.
Write a perfect poem for Yuri.
Write a perfect poem for Natsuki.
Spend enough time during the poem minigame for the music to loop.
Love, Monika
Ruin the game.
Write a perfect poem for Monika.
Start a New Game.