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