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