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