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