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