It is granted for killing 300 creatures. A creature is anything living that isn't human or isn't a non-player character. Robots, radscorpions, super mutants, bloatflies, radroaches, trogs, and feral ghouls all count toward this achievement. A list of "creatures" that can go into the count can be found here.
- One can check progress on this achievement under General and Stats section of the Pip-Boy 3000.
- Killing feral ghouls will result in a creature kill. Non-player character ghouls, like any other non-player character, are not counted as creatures.
- The knife in the achievement is actually transparent instead of white, as when you highlight it, it turns green (Xbox 360).