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