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