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