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