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