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