The last achievement is called "Stay away from Skinner".
To unlock it, you have to unlock all "bubbles" in endless mode, then close the game.


This requires blowing up 10,000 bubbles.
Here is how to unlock the achievement without mindlessly grinding for it.

Your save file can be found at:

NB: if you cannot find the save file there, try the location suggested by SteamDB[steamdb.info]:

It consists in a text file called savedata.ini.

Open this file with your favorite editor for plain text.
Find the line endless_count under the section [gamedata].



Edit the value to 9990. So typically, you should end up with:

Run the game.



Blow up 10 bubbles to reach the 10,000 threshold.