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