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