Here is the full list of all 66 Torchlight achievements. It takes around 100-120 hours to unlock all of the achievements on Windows.
Achieved enlightenment by speaking with the horse 100 times
Defeat Ordrak on Easy Hardcore
Kill 25 champion trolls
Defeat Ordrak on Normal Hardcore
Retire two characters
Retire over 300 levels worth of characters
Reach level 100
Reach the 50th floor of a dungeon
Defeat Ordrak on Hard Hardcore
Complete 200 Quests
Die 500 times
Complete 25 Gar Quests
Kill 50,000 monsters
Drink 5,000 potions
Suffer 20 disenchants from the enchanter
Successfully create 25 items using the transmuter
Successfully enchant one item 10 times
Sell 10,000 items to vendors
Complete 50 Hatch Quests
Use 50 potions on your pet
Collect 250,000 gold
Catch 1000 fish
Beat the game with all three classes
Retire a character
Smash 1500 Breakables
Achieve maximum fame
Take 25,000 steps
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 Ordrak in 8 hours or less
Defeat Ordrak in less than 5 hours
Defeat Alric
Defeat Medea
Achieve player level 100
Achieve player level 65
Defeat Krag
Pull 100 levers
Catch 100 fish
Kill 5000 Monsters
Catch 50 fish
Transform your pet into a Mimic
Have an item disenchanted on the first enchantment attempt
Defeat the Ember Colossus
Do at least 10,000 damage to an enemy in a single strike
Gamble 100 times
Defeat the Root Golem
Defeat the Overseer
Gamble 20 times
Gamble 50 times
Permanently transform your pet
Gamble a unique item
Equip a spell on your pet
Change your pet by feeding it fish
Have 100,000 gold in your inventory
Successfully enchant one item 5 times
Send your pet to town
Defeat Brink
Fill your pet's inventory
Blow 25 enemies to pieces with critical strikes
Find the entrance to the mine
1 game mod installed
5 mods installed at the same time
10 mods used at the same time