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