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