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