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