Here is the full list of all 26 Pocket Mini Golf 2 achievements.
Collect 150 diamonds
Collect 300 diamonds
Collect 500 diamonds
Collect at least 50% of custom balls
Collect at least 50% of custom banners
Collect at least 50% of custom victory animations
Collect at least 50% of custom sound effects
Collect at least 50% of custom trails
Collect 30 stars in aquarium world
Collect 60 stars in aquarium world
Collect 90 stars in aquarium world
Collect all diamond badges in aquarium world
Finish aquarium world
Collect 30 stars in laboratory world
Collect 60 stars in laboratory world
Collect 90 stars in laboratory world
Collect all diamond badges in laboratory world
Finish laboratory world
Collect 30 stars in twilight garden world
Collect 60 stars in twilight garden world
Collect all diamond badges in twilight garden world
Finish twilight garden world
Collect 30 stars in toystore world
Collect 60 stars in toystore world
Collect all diamond badges in toystore world
Finish toystore world