In Rockwell, there's a side mission called Rockwell BBQ. In this, you need to kill # cows (the number increments with every successful completion up to 20). Turn on Deep Thinker and then repeat this, raising the value up to 20. At minimum, 5 at 20 would get you this trophy, but since you have to increase it with previous completions, you'll end up needing to run it about 7 or 8 times total (but the DNA will help too).