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