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