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