Really easy It's Night Cap's
ability. You can do this in the main hub or just playing normally going for you 200 kills with this character.
When activated you will turn invisible and run fast (players will see clouds where you walk so you're not entirely safe, keep that in mind when playing multiplayer). Without too much hassle you will get your achievement in no time.
Wait for a few seconds after each use so the ability has time to recharge.