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