Here is the full list of all 20 Planet Smasher achievements.
Created Uranus
Created Neptune
Created The Earth
Created Venus
Created Mars
Created Mercury
Created Saturn
Created Jupiter
Created The Sun
Created Alpha Centauri
Created Sirius
Created Betelgeuse
Created a Black Hole!
Turn explosion size and volume up to eleven
Win one game on each square grid on easy difficulty
Win one game on each square grid on normal difficulty
Win one game on each square grid on hard difficulty
Win one game on each cubic grid on easy difficulty
Win one game on each cubic grid on normal difficulty
Win one game on each cubic grid on hard difficulty