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