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