The Dawnguard Add-on for The Elder Scrolls V: Skyrim has 10 achievements worth 250 gamerscore.
Complete "Lost to the Ages"
Complete "Awakening"
Complete "Beyond Death"
Complete "Kindred Judgment"
Learn all three words of Soul Tear
Use the special power of Auriel's Bow
Acquire 11 werewolf perks
Acquire 11 vampire perks
Change your face
Defeat a Legendary Dragon