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