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