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