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