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