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.
Clear Argon Corpus dungeon
Kill named bosses on the Arun continent
Clear Akasha's Hideout dungeon
Clear Macellarius Catacombs dungeon
Clear Saravash's Ascent dungeon
Clear Labyrinth of Terror dungeon
Clear Ebon Tower dungeon
Clear Kelsaik's Nest dungeon
Clear Golden Labyrinth dungeon
Clear Sinestral Manor dungeon
Reach level 10
Reach level 20
Reach level 30
Reach level 40
Reach level 50
Reach level 60
Reach level 65
Clear Necromancer Tomb dungeon
Clear Bastion of Lok dungeon
Clear Balder's Temple dungeon
Clear Sabex Armory dungeon
Kill named bosses on the Shara continent
Clear Saleron's Sky Garden dungeon
Clear Cultists' Refuge dungeon
Clear Manaya's Core dungeon