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