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