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