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