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