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