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