Here is the full list of all 34 Brutal TD achievements.
Destroy the first green block
Destroy a screamer block
Destroy the first boss
Break apart a asteroid
Destroy a red blip
Destroy a cash zapper
Destroy the big one
Destroy a ammo zapper
Destroy the green spitter swarm boss
Destroy the inverted yellow boss block
Destroy the spitter swarm boss
Destroy the orange hive boss
Destroy the planets last hope
Destroy a power zapper
Destroy a speed zapper
Encounter the gathering swarm
Encounter the blue wall
Destroy the blue uber blip
Destroy the blue uber block
Destroy the yellow uber blip
Destroy the uber octagon
Destroy the green uber block
Destroy the blue beamer
Destroyed the second planetary defender
Destroy the neon mob
Something is off
Super Meatball
Destroy the tank
Destroy the mothership
Destroy the green uber diamond
Destroy the undying eye
Destroy the swarm
Destroy the red uber block
Destroy the Armored Planet