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