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