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