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