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