Here is the full list of all 25 Block Heads: Instakill achievements.
Get two kills without dying
Get three kills without dying
Get four kills without dying
Get five kills without dying
Get six kills without dying
Get seven kills without dying
Get eight kills without dying
Get nine kills without dying
Win a TDM without getting a kill
Win a TDM
Win a FFA without dying
Win a FFA
Add custom music
Have more than one player work on a level
Publish a level to the Workshop while someone is connected
Publish a level to the Workshop while no one is connected
Start the level builder
Your first kill - with many more to come
Go commit die
Leave a Server
Play with 15 other people
Start customizing your character
Start a server
Join a Server