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