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