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