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