Here is the full list of all 25 TERA achievements worth 1,000 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox One.
Reached level 50
Cleared Golden Labyrinth dungeon
Cleared Necromancer Tomb dungeon
Reached level 40
Cleared Cultists' Refuge dungeon
Cleared Saravash's Ascent dungeon
Cleared Sinestral Manor dungeon
Reached level 30
Cleared Bastion of Lok dungeon
Reached level 20
Reached level 10
Clear Argon Corpus dungeon
Kill named bosses on the Arun continent
Clear Akasha's Hideout dungeon
Clear Macellarius Catacombs dungeon
Clear Labyrinth of Terror dungeon
Clear Ebon Tower dungeon
Clear Kelsaik's Nest dungeon
Reach level 60
Reach level 65
Clear Balder's Temple dungeon
Clear Sabex Armory dungeon
Kill named bosses on the Shara continent
Clear Saleron's Sky Garden dungeon
Clear Manaya's Core dungeon