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