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