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