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