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