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