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