Observe.

1. 
   Urban Explorer

   Unlocked by completing the "Town" level.
   100%
2. 
   Beneath It All

   Unlocked by completing the "Sewer" level.
   50%
3. 
   The Deep End

   Unlocked by completing the "Poolrooms" level.
   33%
4. 
   Why, Hello There.Secret

   Steam withholds the description of a secret achievement.
   100%
5. 
   Noisy NeighborSecret

   Steam withholds the description of a secret achievement.
   83%
6. 
   Happy Birthday..Secret

   Steam withholds the description of a secret achievement.
   50%
7. 
   ParanoidSecret

   Steam withholds the description of a secret achievement.
   33%
8. 
   The Basics

   Finished the tutorial.
   50%
9. 
   HAHAHAHAHAHAH!!!!Secret

   Steam withholds the description of a secret achievement.
   33%
10. 
    The End.Secret

    Steam withholds the description of a secret achievement.
    17%

Names, descriptions and icons are the game’s own, as Steam publishes them; the share is how many owners have unlocked each, from Steam's global figures for 10 of them.