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