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