Really easy and surprisingly satisfying. Once you get the ability to spawn vehicles with the catch-a-ride, simply drive around and roadkill any bandit or skag you find until this trophy pops.
*NOTE every time you hit an enemy you will damage your vehicle so keep an eye on how much you're doing or you might find yourself in a bad spot with no ride out if you take too much. Your vehicle will repair itself over time after it stops taking damage for a few seconds.