Here is the full list of all 66 Torchlight achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Defeat Ordrak on Normal Hardcore
Defeat Ordrak in 8 hours or less
Defeat Ordrak in less than 5 hours
Find the entrance to the mine
Fill your pet's inventory
Have 100,000 gold in your inventory
Blow 25 enemies to pieces with critical strikes
Equip a spell on your pet
Transform your pet into a Mimic
Successfully enchant one item 10 times
Permanently transform your pet
Send your pet to town
1 game mod installed
5 mods installed at the same time
10 mods used at the same time
Gamble a unique item
Achieve player level 65
Achieve player level 100
Pull 100 levers
Achieve maximum fame
Kill 5000 Monsters
Defeat the Root Golem
Defeat the Ember Colossus
Defeat Krag
Defeat Ordrak on Very Hard Hardcore
Complete 50 Hatch Quests
Drink 5,000 potions
Die 500 times
Sell 10,000 items to vendors
Catch 1000 fish
Reach level 100
Kill 25 champion trolls
Kill 50,000 monsters
Reach the 50th floor of a dungeon
Defeat Ordrak on Easy Hardcore
Defeat Ordrak on Very Hard
Complete 25 Gar Quests
Complete 200 Quests
Beat the game with all three classes
Suffer 20 disenchants from the enchanter
Defeat Alric
Smash 1500 Breakables
Use 50 potions on your pet
Catch 100 fish
Catch 50 fish
Have an item disenchanted on the first enchantment attempt
Defeat Ordrak on Hard
Defeat Ordrak on Hard Hardcore
Retire two characters
Retire over 300 levels worth of characters
Gamble 100 times
Do at least 10,000 damage to an enemy in a single strike
Retire a character
Successfully create 25 items using the transmuter
Gamble 20 times
Gamble 50 times
Defeat Ordrak with no deaths
Defeat Ordrak on Easy or Normal
Defeat Medea
Collect 250,000 gold
Take 25,000 steps
Achieved enlightenment by speaking with the horse 100 times
Defeat the Overseer
Successfully enchant one item 5 times
Defeat Brink
Change your pet by feeding it fish