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