Here is the full list of all 20 Grass Cutter - there are Mutated Lawns achievements worth 1,000 gamerscore.
25 times, purchase 15% of the energy
Face the monsters 50 times
Disable 50 monsters
Eliminate robot
Eliminate multiple monsters in less than 1 second
Drive by 10 times on the sand
Make the first purchase
Scare the dogs 20 times
Use a bomb
Eliminate quadcopter
Get wet in the rain
Take a mud bath 20 times
Gather up energy when there is less than 5% left
Cut 1000 squares with grass
Immerse the first box
Dive into the water 20 times
Break 100 barriers
Scare the birds 50 times
Scare the cats 15 times
Complete the first level