Here is the full list of all 20 Space Robot Samurai Zombie Slayer achievements.
Clear the Screen
Take No Damage for 1 Minute
Kill 20000 Zombies
Kill 10000 Zombies
Get Killed With 10 or Less Points
Accumulate 1000000 Points All Time
In This Game You Kill Zombies
Get a 99x Streak
Get 100000 Points in a Single Game
Kill 1000 Zombies
Get a 50x Streak
Survive for the Entire Song
Take 100 Damage in a Single Game
Survive for a Wave
Get 10000 Points in a Single Game
Take 50 Damage in a Single Game
Get 1000 Points in a Single Game
Kill 100 Zombies
Get a 10x Streak
Kill 1 Zombie