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