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