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