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