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