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