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