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