Here is the full list of all 66 Torchlight achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Retire over 300 levels worth of characters
Die 500 times
Complete 50 Hatch Quests
Kill 25 champion trolls
Kill 50,000 monsters
Suffer 20 disenchants from the enchanter
Drink 5,000 potions
Reach level 100
Defeat Ordrak on Normal Hardcore
Defeat Ordrak on Hard Hardcore
Achieve player level 100
Defeat Ordrak on Easy Hardcore
Sell 10,000 items to vendors
Catch 1000 fish
Smash 1500 Breakables
Achieved enlightenment by speaking with the horse 100 times
Transform your pet into a Mimic
Retire two characters
Beat the game with all three classes
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
Complete 200 Quests
Gamble 100 times
Catch 100 fish
Reach the 50th floor of a dungeon
Achieve maximum fame
Catch 50 fish
Complete 25 Gar Quests
Achieve player level 65
Do at least 10,000 damage to an enemy in a single strike
Gamble 50 times
Successfully enchant one item 10 times
Successfully enchant one item 5 times
Gamble 20 times
Have an item disenchanted on the first enchantment attempt
Use 50 potions on your pet
Collect 250,000 gold
Gamble a unique item
Defeat Ordrak on Easy or Normal
Defeat Alric
Have 100,000 gold in your inventory
Defeat Medea
Defeat Krag
Kill 5000 Monsters
Defeat the Ember Colossus
Defeat the Root Golem
Successfully create 25 items using the transmuter
Take 25,000 steps
Defeat the Overseer
Pull 100 levers
Defeat Brink
Equip a spell on your pet
Send your pet to town
Fill your pet's inventory
Blow 25 enemies to pieces with critical strikes
10 mods used at the same time
Change your pet by feeding it fish
Permanently transform your pet
5 mods installed at the same time
1 game mod installed
Find the entrance to the mine