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