Here is the full list of all 27 BUTCHER achievements.
Impale 25 enemies on hook by kicking them.
Unlock new difficulty mode.
Find 20 skulls.
Find 10 skulls.
Complete the game on "Hard" difficulty.
Maul 200 enemies to death with a sawspider.
Repeat a single level 10 times.
Beat The Last City.
Kill 10 enemies with a single railgun bullet.
Beat Volcano Research Station.
Beat Jungle Outpost.
Kill 1000 enemies.
Make 200 enemies die horribly by burning alive.
Beat Old Military Base.
Beat Ironworks Facility.
Find 30 skulls.
Find all skulls.
Complete the game on "Harder" difficulty.
Complete the game on "The Hardest" difficulty.
Complete the game in 1 hour on at least HARD difficulty.
Die 200 times in total.
Impale 50 enemies on hook by kicking them.
Complete the game in 45 minutes on at least HARD difficulty.
Complete the game in 1.5 hour on at least HARD difficulty.
Upload your level pack to the Workshop.