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