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