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