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