Here is the full list of all 51 Snuff achievements.
Escape the Corperation.
Kill Jeffrey Hatcher
Kill Pedro Garavito
Kill Erik Poulsen
Kill Robert Sinclair
Kill Naceur Mesfewi
Kill Gamal Randitsheni
Kill Fekadu Amanyire
Kill Szilveszter Fazekas
Kill Mikhail Ryakhovsky
Kill Devendra Jaishankar
Kill Pusok Sobhraj
Kill John Eric Wagner
Kill Yoshio Nakamura
Pass the dark Forest.
Enter the final Gate.
Defeat the Devil.
Find all Secrets in the United States.
Find all Secrets in South America.
Find all Secrets in Greenland.
Find all Secrets in Great Britain.
Find all Secrets in Algeria.
Find all Secrets in South Africa.
Find all Secrets in Somalia.
Find all Secrets in Hungary.
Find all Secrets in Russia.
Find all Secrets in India.
Find all Secrets in Malaysia.
Find all Secrets in Australia.
Find all Secrets in Japan.
Find every Secret in all Levels.
Kill two Enemies with one Shot.
Kill three Enemies with one Shot.
Kill three Enemies with one explosive Barrel.
Cut of 1000 Limbs.
Defeat the game on journalist or higher difficulty.
Defeat the game on flowergirl or higher difficulty.
Defeat the game on mortal or higher difficulty.
Defeat the game on natural born killer or higher difficulty.
Defeat the game on death march or higher difficulty.
Defeat the game on snuff difficulty.
Kill 24 Enemies.
Kill 100 Enemies.
Kill 1.000 Enemies.
Kill 10.000 Enemies.
Kill 100.000 Enemies.
Smash 10 Heads.
Smash 100 Heads.
Smach 1.000 Heads.
Smash 10.000 Heads.
Smash 100.000 Heads