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