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