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