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