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
Fill your pet's inventory
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
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 100 times
1 game mod installed
5 mods installed at the same time
10 mods used at the same time
Gamble a unique item
Achieve player level 65
Achieve player level 100
Retire a character
Pull 100 levers
Take 25,000 steps
Defeat Brink
Defeat the Overseer
Defeat the Root Golem
Defeat the Ember Colossus
Defeat Krag
Defeat Medea
Defeat Alric
Defeat Ordrak with no deaths
Defeat Ordrak on Very Hard
Defeat Ordrak on Easy Hardcore
Defeat Ordrak in 8 hours or less
Defeat Ordrak in less than 5 hours
Complete 50 Hatch Quests
Defeat Ordrak on Hard Hardcore
Sell 10,000 items to vendors
Defeat Ordrak on Normal Hardcore
Catch 1000 fish
Reach level 100
Kill 25 champion trolls
Defeat Ordrak on Very Hard Hardcore
Die 500 times
Suffer 20 disenchants from the enchanter
Use 50 potions on your pet
Kill 50,000 monsters
Retire over 300 levels worth of characters
Drink 5,000 potions
Achieved enlightenment by speaking with the horse 100 times
Achieve maximum fame
Retire two characters
Defeat Ordrak on Hard
Complete 200 Quests
Successfully enchant one item 10 times
Complete 25 Gar Quests
Smash 1500 Breakables
Have an item disenchanted on the first enchantment attempt
Beat the game with all three classes
Gamble 50 times
Have 100,000 gold in your inventory
Collect 250,000 gold
Gamble 20 times
Defeat Ordrak on Easy or Normal
Successfully enchant one item 5 times
Kill 5000 Monsters
Equip a spell on your pet
Blow 25 enemies to pieces with critical strikes