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