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