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