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