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