Here is the full list of all 25 BUTCHER achievements worth 1,000 gamerscore.
Find all skulls.
Beat The Last City.
Find 30 skulls.
Kill 10 enemies with a single railgun bullet.
Beat Volcano Research Station.
Impale 50 enemies on hook by kicking them.
Impale 25 enemies on hook by kicking them.
Unlock new difficulty mode.
Find 20 skulls.
Beat Jungle Outpost.
Repeat a single level 10 times.
Maul 200 enemies to death with a sawspider.
Kill 1000 enemies.
Find 10 skulls.
Make 200 enemies die horribly by burning alive.
Beat Old Military Base.
Beat Ironworks Facility.
Complete the game in 1.5 hour on at least HARD difficulty.
Complete the game in 45 minutes on at least HARD difficulty.
Complete the game on "Hard" difficulty.
Complete the game on "Harder" difficulty.
Complete the game on "The Hardest" difficulty.
Complete the game on "Impossible" difficulty.
Complete the game in 1 hour on at least HARD difficulty.
Die 200 times in total.