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