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