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