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