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