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