The Undead Nightmare Pack Add-on for Red Dead Redemption has 12 achievements worth 200 gamerscore.
Complete "Cure For Most of What Ails You" and "Get Back in that Hole, Partner" Survivor Missions.
Find and kill a sasquatch.
Complete "Curious Tales from Blackwater, USA" Survivor Mission.
Complete "Mother Superior Blues" Survivor Mission.
Complete "On a Pale Horse".
Have every territory saved at the same time during the Undead Nightmare.
Attain 100% Game Completion statistic in Undead Nightmare.
Attain Rank 5 in all Undead Nightmare Challenges.
Find and break a unicorn.
Find and kill a chupacabra.
Make it to wave 15 in Undead Overrun Gametype in Multiplayer.
Fight off 8 unique players during your time on top during Land Grab in Multiplayer Free Roam.