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