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