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