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