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