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