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