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