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