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