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