Here is the full list of all 12 Stick Em Up 2: Paper Adventures achievements.
Destroy four enemies with one spear on expert
Complete all levels on beginner or higher
Complete all levels on regular or higher
Destroy four enemies with one spear
Destroy all the equipment that can be destroyed on Headquarters in 1P mode
Spin the moon rover through 720 degrees and land the right way up
Get a golden score (destroy every enemy and don't get hit) on every level on regular or higher
Finish Apollo in 1P mode on expert without firing any rockets or losing any health (it's okay if the rover gets destroyed, though)
Complete all levels on expert
Spin the moon rover through 1440 degrees (four turns) and land the right way up
Finish Japan in 1P mode on beginner without firing or losing any health
Get a golden score (destroy every enemy and don't get hit) on every level on expert