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