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