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