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