Blow up 50 explosive objects.
Throughout the game you will find explosive items all over the place. If you can blow it up and cause some damage to an enemy or yourself it counts towards this achievement. Shoot Gas Tanks, Fire Extinguishers, Propane Tanks, Compressed Gas Cylinders and anything else you can find that explodes. If you don't reach this required amount by the time you hit the docks, you will find enough explosive items around this level.
Alternatively you can keep replaying the start of Red Meat and destroy the three fire extinguishers at the start of the level over and over.