Here is the full list of all 16 Magnet Crusher achievements.
Reach level 5 in Arcade mode
Reach level 10 in Arcade mode
Reach level 20 in Arcade mode
Unlock a bonus level
Vanquish the Fortress
Vanquish the Hexatank
Vanquish the Blinker
Vanquish the Knight
Destroy 1 000 enemies
Destroy 10 000 enemies
Destroy 100 000 enemies
Acquire 1 skin
Destroy 200 enemies without taking any damage
Unlock 8 abilities
Unlock 1 ability
Destroy 10 enemies in a row