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