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