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