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