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