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