Here is the full list of all 39 Gal*Gun: Double Peace achievements.
View Kurona's True Ending
View Ekoro's True Ending
View Sisters Route's True Ending
Receive a “Perfect!” Score VS Shinobu & Maya
Get a Perfect Score on “Demon-Attracting Balm”
Get a Perfect Score on “Sisters' Odd Ritual”
View Aoi's Ending
View Shinobu's True Ending
Receive a “Perfect!” Score VS Shinobu
Receive a “Perfect!” Score VS Mr. Demon Veggie
View Maya's True Ending
Fulfill 10 of the Girls' Requests
Get a Perfect Score on “Maya's Demon Calling”
Get a 30 Combo of Ecstasy Shots
View Your First Ending
Experience Your First Final Doki-Doki Mode
Give 500 Girls Euphoria
Get a Perfect Score on “Her Majesty Shinobu”
Fire 1000 Pheromone Shots
Get a Perfect Score on “Shinobu in the Window”
Get 100 Ecstasy Shots
Experience Your First Doki-Doki Mode
Give a Girl Euphoria
Unlock All Trophies
View Patako's True Ending
View the True Love Route's True Ending
View All of the True Endings
Get a Perfect Score on “Maya's Medical Care”
Receive a “Perfect!” Score VS Maya
Receive a “Perfect!” Score VS Ekoro
Receive a “Perfect!” Score VS Kurona
Receive a “Perfect!” Score VS Patako
Receive a “Perfect!” Score VS Mr. Demon Balloon
Defeat 100 Demon Girls
Make 50+ Girls Experience “Double Peace”
Collect All of the Panties From the Changing Room
Obtain All Images in the Gallery
Complete Profiles for Every Girl
Achieve Godlike Rank