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