For this achievement you need to grab 2 keycards from guards. The first guard's area is marked on your map. Head there and look to a container suspended in air, where there will be a dead guard still attached to his parachute. The next guard will be directly west from the next waypoint's location, on a rooftop surrounded by thugs (look for his red/white striped parachute). As soon as you start talking to Nightwing on the radio the achievement will unlock.