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