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