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