Overkill

Overkill is a one-star (★) challenge added in the Fallout: New Vegas add-on Gun Runners' Arsenal.

Obtaining
You must kill any animal with either a Fat Man or a Fat mine to complete this challenge.

'Mutated animals' like gecko, brahmin, or bighorners do not count, only regular animals. Unfortunately, in the wake of nuclear war, the only 'animals' are coyotes and all types of dog, including NCR and Legion dogs.