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