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