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