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