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