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