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