Here is the full list of all 10 Kinect Sports Gems: Darts vs. Zombies achievements worth 50 gamerscore.
Reach level 10 (or observe another player doing so) to gain the rank of Earth's Last Hope.
Reach level 9 (or observe another player doing so) to gain the rank of Zombie Nemesis.
Reach level 8 (or observe another player doing so) to gain the rank of Undead Exterminator.
Wicked aim! You reached level 7 (or observed another player doing so) for promotion to Dart Demon.
Nailed! You reached level 6 (or observed another player doing so) to become a Walking Dead Stopper.
Shots fired! You reached level 5 (or observed another player doing so) to progress to Zombie Hunter.
On target! You reached level 4 (or observed another player doing so) to rank as Dart of the Dead.
Face your fears! You reached level 3 (or observed another player doing so), rising to Zombie Hugger.
Resilient! You reached level 2 (or observed another player doing so) and made it to Scared Survivor.
First steps! You reached level 1 (or observed another player doing so) for the title of Zombie Nerd.