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