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