Here is the full list of all 30 Terraria achievements worth 400 gamerscore. It takes around 80-100 hours to unlock all of the achievements on Xbox 360.
You have defeated every boss!
You have smelted 10,000 bars of metal!
Your World is Corrupt!
Your World is Hallowed!
You have obtained every type of armor.
You seem to like pets.
You have defeated Skeletron Prime!
You have defeated The Twins!
You have defeated The Destroyer!
You are a master smith!
You have used every crafting station!
You have killed every type of slime!
Every NPC has moved in!
You have unlocked Hard Mode!
You have the maximum health and mana!
You have placed 100 wires!
You have defeated the Goblin Army!
Enjoy the view.
You have survived the Blood Moon!
You have traveled over 42km on the ground!
You are ready for battle!
You have reached the bottom of the World!
You have gone to The Underworld and back without dying!
You have removed more than 10,000 blocks!
Looking good!
The Guide has moved in!
You can only go down from here!
You have survived the first night!
You have completed the tutorial!
You have begun the tutorial!