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