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