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 are a master smith!
You have defeated The Twins!
You have defeated The Destroyer!
You have killed every type of slime!
You have placed 100 wires!
You have used every crafting station!
Every NPC has moved in!
You have unlocked Hard Mode!
You have the maximum health and mana!
You have defeated the Goblin Army!
Enjoy the view.
You have traveled over 42km on the ground!
You have removed more than 10,000 blocks!
Looking good!
You have survived the Blood Moon!
You have gone to The Underworld and back without dying!
You have reached the bottom of the World!
You are ready for battle!
You can only go down from here!
The Guide has moved in!
You have survived the first night!
You have completed the tutorial!
You have begun the tutorial!
Defeat every boss.
Corrupt most of the World.
Hallow most of the World.
Defeat Skeletron Prime.
Find ALL the pets.
Smelt 10,000 bars of metal.
Obtain every type of armor.