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