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