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