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