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