Here is the full list of all 69 Deep Space Waifu: FLAT JUSTICE achievements. It takes around 2-3 hours to unlock all of the achievements on Windows.
Complete ONE HANDED MILF
Find the PERFECT FLATNESS
DATE all girls
Finish with the M.I.L.F.
Defeat Dickus final form
100% M.I.L.F.
complete ONE HANDED SPY
Infiltrate in the secret TENTACLE organization
Destroy the Sneak Mothership
complete 100% the spy
Complete ONE HAND SERGEANT CHIKARA
Defeat DP Miner
100% SERGEANT CHIKARA
Complete ONE HAND LIME CODE
Unlock M.I.L.F.
Get the super scret spy business card
Defeat Dickus third form
100% LIME CODE
Be spotted by the enemy
Unlock the SECRET SPY
Complete ONE HAND NORMAL ROCKY CHAN
Defeat the Thrasher Super Mecha Warrior
Complete NORMAL ROCKY-CHAN
Complete ONE HAND PUCKY K-9 UNIT
Unlock SERGEANT CHIKARA
Get the F.L.A.T. Multipass badge
Reach 30 STARS
Defeat Dickus second form
100% PUCKY K-9 UNIT
Unlock LIME CODE
Complete ONE HAND METAL ROCKY CHAN
100% METAL ROCKY CHAN
Complete an ONE HANDED SALE
Complete SAYRU-CHAN
Defeat DP Mothership
Complete ONE HANDED SHARP-EYE
Unlock NORMAL ROCKY-CHAN
Get promoted to the F.L.A.T. SPECIAL FORCES
Get a smelling Pantie evidence
Reach 18 STARS
Defeat the Fake Wadding
100% SHARP-EYE YUMIKO
Unlock PUCKY K-9 UNIT
Complete ONE HAND NAO
Defeat DP Defender
100% NAO NEKOYAMA
Get the SHIELD power up
Explode a mine!
Complete ONE HAND JULIA
Unlock METAL ROCKY-CHAN
Unlock SAYRU-CHAN
Get a special Phone Number
Reach 10 STARS
Defeat Dickus first form
100% JULIA SUZUHARA
Make a 5 STARS stage
Get the MACHINE GUN power up
Get the RAY power up
Unlock SHARP-EYE YUMIKO
Complete ONE HAND MIKA
Use the JUSTICE LASER special attack
Take a photo of a girl
Kick Justice in the balls
100% MIKA MOKOTO
Get the LASER power up
Get the ROCKET LAUNCHER power up
Torn apart your first piece of cloth
Go to your first date
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