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