Here is the full list of all 9 Comet Crasher achievements.
Maintain full Power for 30 seconds straight
Have three powerups active at the same time
Set off a chain of 11 bombs or more
Shoot 10 mines just before you would've hit them
Get launched into a mine by a bumper
With a single Laser shot, wipe out 50 blocks or more
Break 25,000 blocks across all games
Reach the Gravity Well
Reach the Gravity Well without taking damage