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