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