Here is the full list of all 24 Guardian: Planet Defense achievements.
Destroy 100 Asteroids
Destroy 500 Asteroids
Destroy 1,000 Asteroids
Destroy 5,000 Asteroids
Destroy 10,000 Asteroids
Complete 5 waves in a single game
Complete 10 waves in a single game
Complete 15 waves in a single game
Complete 20 waves in a single game
Complete 25 waves in a single game
Complete 30 waves in a single game
Complete 35 waves in a single game
Complete the first wave!
Complete an entire wave using only a single shot per asteroid
Destroy an asteroid with an explosion
Destroy two asteroids with chained explosions
Destroy three asteroids with chained explosions
Destroy four asteroids with chained explosions
Kill the first boss asteroid