Here is the full list of all 39 LEGO The Hobbit achievements. It takes around 35-40 hours to unlock all of the achievements on Windows.
Collect 10,000,000,000 studs. (Single Player Only)
Achieve 100% completion
Complete all the quests in Middle-earth. (Single Player Only)
Transform to Beorn's bear form.
Collect all characters. (Single Player Only)
Forge all the Perfect Mithril Treasure Items. (Single Player Only)
Forge all the Mithril Treasure Items. (Single Player Only)
Collect all Mithril Bricks. (Single Player Only)
Use every Dwarf from Thorin's Company in a Buddy-Up attack
Equip yourself with Dazzle Wig, Mithril Rhythm Stick and Mithril Dance Boots.
Equip Thorin with the Mithril Mushroom Crown
Use Gandalf's startle ability to dazzle 50 enemies
Use 50 Buddy-Up attacks
Collect all Schematics. (Single Player Only)
Collect all Minikits. (Single Player Only)
Collect all Treasure Items in levels. (Single Player Only)
Obtain all Master Burglar titles. (Single Player Only)
Complete the Bonus Level
Complete ''Inside Information''
Complete ''On the Doorstep''
Complete ''The Necromancer''
Complete ''Barrels Out of Bond''
Complete ''A Warm Welcome''
Complete ''Looking for Proof''
Complete ''Flies and Spiders''
Create a custom character.
Complete ''Queer Lodgings''
Complete ''Out of the Frying Pan…''
Obtain 150,000 studs from Instruction Builds bonuses. (Single Player Only)
Complete ''Goblin Town''
Complete ''Over Hill and Under Hill''
Complete ''The Troll Hoard''
Complete ''Roast Mutton''
Complete the mining game perfectly 50 times
Complete ''Azog the Defiler''
Collect 99 of any loot
Play a level in co-op
Complete ''An Unexpected Party''
Complete ''Greatest Kingdom in Middle-earth''