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