Here is the full list of all 37 Gal*Gun 2 achievements.
Reach the ending for the first time.
Finish Chiru's route A.
Give 50 girls euphoria with Lovestrikes.
Take a good look from below when you have a girl over.
Get stepped on by 50 girls.
Get kissed by 10 girls.
Clear all of the Kamizono Sisters' requests.
Give 30 girls Striphoria.
Get stepped on by 10 girls.
Clear your first Doki Dokie Mode.
Call a girl over to your house for the first time.
Suck up 500 mini-demons.
Use the Demon Sweeper to give a girl Striphoria for the first time.
Give 500 girls euphoria.
Clear your first defense mission.
Clear your first search mission.
Suck up a Metal Kurona for the first time.
Suck up 100 mini-demons.
Give 100 girls euphoria.
Give a girl a snack for the first time.
Get 50 ecstacy shots in a row.
Get 30 ecstacy shots in a row.
Clear your first regular mission.
Perform a Lovestrike for the first time.
Get an ecstacy shot for the first time.
Unlock all other achievements.
Reach Risu's good ending.
Finish Nanako's route A.
Finish Nanako's route B.
Finish Chiru's route B.
Reach the Harem ending.
Upgrade your Pheromone Goggles to their final form.
Upgrade your Demon Sweeper to its final form.
Get every girls' phone number.
Get kissed by 50 girls.
Have plenty of conversations with Chiru.
Have plenty of conversations with Nanako.