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