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