Here is the full list of all 12 Shank achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
Complete Single Player Campaign on Normal Mode
Complete Single Player Campaign on Hard Mode
Complete Co-op Campaign Mode
Defeat El Raton
Defeat The Butcher
Defeat Cassandra
Defeat The Priest
Defeat Cesar
Take out 20 enemies
Take out 100 enemies
Take out 1000 enemies
100 Chainsaw kills