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