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