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