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