Here is the full list of all 119 Torchlight II achievements. It takes around 200 hours to unlock all of the achievements on Windows.
Sell 50,000 items
Break 10,000 breakables
Fish 1,000 times
Deal 100,000 critical strikes
Defeat the Nether King with each of the 4 classes
Defeat the Nether King as a Berserker
Use 100 maps
Have 10,000,000 gold
Use 5,000 potions
Defeat the Nether King as an Embermage
Defeat the Nether King in hardcore mode (casual)
Defeat the Nether King in hardcore mode (elite)
Defeat the Nether King in hardcore mode (normal)
Defeat the Nether King in hardcore mode (veteran)
Find 100 secret rooms
Use 10 maps
Use an enchanter 500 times
Die with a hardcore character
Purchase 100 items from the gambler
Defeat the Nether King as an Engineer
Socket 500 gems into items
Purchase 50 items from the gambler
Purchase 20 items from the gambler
Have 50 friends
Have 10 friends
Use a map
Sell 5,000 items
Reach level 100
Destroy 100 socketed gems
Obtain a tier 3 skill bonus
Have 1,000,000 gold
Use an enchanter 50 times
Add a friend
Squish 1000 critters
Defeat 500 champions
Deal 10,000 critical strikes
Explode 10,000 enemies
Start a hardcore character
Begin new game plus
Defeat the Nether King in Casual difficulty
Defeat the Nether King in Elite difficulty
Defeat the Nether King in Normal difficulty
Defeat the Nether King in Veteran difficulty
Defeat the Nether King as an Outlander
Defeat the Nether King
Defeat the Dark Alchemist
Defeat Aleera
Defeat Marishka
Defeat Verona
Assemble TrillBot
Defeat Killbot
Find a legendary item
Defeat Vyrax
Do 10,000 damage with a single attack
Find 10 secret rooms
Defeat Thiss
Defeat Cacklespit
Squish 500 critters
Defeat Bloatfang
Recover 100 gems from items
Defeat the Grizzled Alpha
Defeat the Wraith Lord
Take 100,000 steps
Break 1,000 breakables
Fish 100 times
Have 100,000 gold
Defeat Boletus Rex
Obtain a tier 2 skill bonus
Defeat the Siege Guardian
Defeat Ezrek Khan
Defeat Aruk
Defeat the King In Masks
Open 500 chests
Use 500 potions
Learn 4 spells
Socket 50 gems into items
Teach a pet 4 spells
Destroy 10 socketed gems
Take 50,000 steps
Defeat the Artificer
Recover 10 gems from items
Deal 1,000 critical strikes
Defeat the Manticore's Mate
Defeat the Manticore
Squish 100 critters
Defeat 100 champions
Sell 500 items
Explode 1,000 enemies
Use an enchanter 10 times
Recover a gem from an item
Defeat Grand Regent Eldrayn
Use 50 potions
Defeat Chillhoof
Open 100 chests
Defeat 25 champions
Defeat King Pogg
Defeat Kidrik the Mauler
Teach a pet a spell
Defeat the Winter Widow
Destroy a socketed gem
Defeat General Grell
Take 10,000 steps
Break 100 breakables
Find a secret room
Explode 100 enemies
Fish 10 times
Fish using dynamite
Trade an item with another player
Defeat Mordrox
Obtain a tier 1 skill bonus
Learn a spell
Start a multiplayer game
Defeat One-Eyed Willy
Socket a gem into an item
Open 20 chests
Send your pet to town
Wear a completed armor set
Defeat the Fallen Guardian
Join a multiplayer game