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