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