Here is the full list of all 48 LEGO The Lord of the Rings achievements. It takes around 30-35 hours to unlock all of the achievements on Windows.
Fish perfectly 20 times by pressing the icon as it flashes.
Unlock all the Map Stones in Middle-earth. (Single Player Only)
Collect more than 10,000,000,000 studs. (Single Player Only)
Travel to Isengard as every playable Hobbit.
Turn an enemy into a skeleton and make them dance.
Defeat Gollum as Gollum.
Travel to Trollshaws as Bilbo.
Get 100%. (Single Player Only)
Unlock all characters. (Single Player Only)
Complete the Bonus Level.
Craft every Mithril item. (Single Player Only)
Collect all the Mithril Bricks. (Single Player Only)
Complete all the Fetch Quests in Middle-earth. (Single Player Only)
Collect all the Red Bricks. (Single Player Only)
Dress a character completely in treasure items.
Craft the Fire and Ice Bows. (Single Player Only)
Use the Ent Draught on Pippin.
Defeat 42 Uruk-hai as Legolas.
Equip Aragorn with the Mushroom Crown.
Complete 'The Mines of Moria' in under 15 minutes.
Achieve True Adventurer in every level. (Single Player Only)
Complete a level in co-op.
Throw Gimli 30 times.
Walk into Mordor.
During 'Prologue', jump into the fires of Mount Doom as Isildur.
Complete 2 cooking puzzles.
Complete 'Mount Doom'.
Complete 'The Black Gate'.
Complete 'The Battle of Pelennor Fields'.
Complete 'Taming Gollum'.
Complete 'The Dead Marshes'.
Complete 'Track Hobbits'.
Complete 'Warg Attack'.
Complete 'Helm's Deep'.
Complete 'Osgiliath'.
Complete 'The Secret Stairs'.
Complete 'Cirith Ungol'.
Complete 'The Paths of the Dead'.
Finish one of Gimli's opponents as Legolas in 'Helm's Deep'.
Defeat an Oliphaunt as Legolas.
Complete 'Amon Hen'.
Reach the top of Amon Hen without being caught once by Boromir. (Single Player Only)
Complete 'The Mines of Moria'.
Complete 'The Pass of Caradhras'.
Form The Fellowship of the Ring.
Complete 'Weathertop'.
Complete 'The Black Rider'.
Complete 'Prologue'.