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