Here is the full list of all 23 Ben and Ed - there are Blood Party achievements.
Survive 10 minutes as head.
Never give up!
Survive one minute as head.
Finish a race headless.
Finish the tutorial.
Build your own map.
Create Ed
Beat all singleplayer maps.
Find Hans.
Inject acid into 20 enemies.
Cut off 10 parts of your enemies.
Cut off 100 parts of your enemies.
Cut off 1000 parts of your enemies.
Survive 60 minutes as head.
Produce 10 meatblocks.
Produce 100 meatblocks.
Produce 1000 meatblocks.
Hold on to chickens for 1 minute.
Hold on to chickens for 10 minutes.
Hold on to chickens for 30 minutes.
Meet Ben.
Place 50 Trashcans.