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